I like to use the metaphor of peaking when talking about highly productive times at different stages of your academic career. Think of these peaks as the high-water marks (i.e., year your most high profile papers came out any you get a new grant). These peaks are preceded by periods of high data gathering and much writing; and followed by periods of transition, where new methods are being learned, and the finishing touches are put on loose ends of major projects. I think these peaks should come every three to five years and they are important milestones in your academic career. The first major peak should be around the 3rd year of your PhD program, another sometime during your postdoc, and your highest peak should be during the midpoint of your time as an assistant professor (3rd year pre-tenure or so). There are other peaks (e.g. just before going up for associate and full professor) but let’s talk about the three majors ones in more detail.
When you are starting off in grad school (let’s assume a PhD program), you want to be a sponge learning new techniques and gathering data over the first couple of years. As you learn to write during these years it usually takes until at least your 3rd year until the publications from those early works start coming out. That’s a good thing because that’s usually the time you go up for your qualifying exams (to be a PhD candidate in good standing). The students that have some pubs coming around this time are usually on the fast track. Those pubs will be some thesis chapters, but also collaborative side projects with others. Once you reach this peak, the thesis committee usually is okay with passing you for these qualifying exams making you a PhD candidate. After that peak, students typically focus on the meatier sections of their thesis and getting them ready for publication.
Another peak should come at some point during a postdoc. You’ve learned some new skills as a graduate student, and those techniques will make you marketable to others. After you get a postdoc, you won’t need to worry about the constraints you had in graduate school like classes, or friendships (just kidding here, but usually postdocs are kind of in limbo in their new short-term work environment, so friends are harder to come by for sure). Without these constraints you should hit the ground running and publish like mad, collaborating with your new lab, finishing up old projects, getting your last thesis chapters published. This peak should push you out onto the job market.
So you got a job, time to finish your own personal Mount Everest climb of academic peaks. As you get your new desk tidy, turn on your new computer for the first time, and figure out how to order everything from pens to major lab equipment, you should also be setting yourself up for big peak around the midpoint of your time before you go up for tenure (again around the 3rd year). Your pubs from your postdoc should be coming out (always include your new and old address on these pubs) but also the new cool things you started on at your new position; those things you always wanted to try but didn’t have the independence to attempt. It is all those ideas you put together for your “future plans” slides in your job talk that are coming to fruition. During your first and second year of your job you should have a good bit of start-up to spend and hopefully you have been applying for grants at this time. If you get that grant before your start-up runs out you are in good shape. This time should be the most productive period of your career, you still have postdoc skills, but you also have your own lab, and those people are being productive as well feeding off your ideas and plans.These peaks aren’t set in stone at these different time periods but I like to think of them as goals you are trying to reach. Of course you can have a brilliant career peaking at very different times but you don’t want to have your highest peak as a postdoc, or in grad school and Peter out at your new job. And of course these recommendations are just based on personal observations of people’s work and career paths that I’ve generalized here. Sometimes new graduate students get impatient and discouraged about the pace at which publications are coming out, so I always tell them it is important to be patient and that it really isn’t until their 3rd year that we expect them to really be getting those pubs coming out at a regular clip. Likewise, a postdoc with no pubs for a few years certainly isn’t peaking, and almost certainly isn’t getting a tenure-track job anytime soon. A new faculty member in his/her 4th year without a grant and with few pubs might have quite a few things come out in Year 5 but by then the voting faculty will already be thinking of that person with whispers of them not having the stuff to get tenure. That person might still get tenure with the last minute drive but that late peek will be remembered and sometimes considered a negative (e.g. they might say, "This person couldn’t get their stuff together in time for their 3rd year pre-tenure review. Will they be a good scientist with tenure?"). So yes these peaks are generalizations but they are good things to keep in mind as you move up the academic landscape with all its peaks and valleys.