I've been doing 2 peaks a season, typically 4 weeks each. The second peak tends to go possibly a little longer depending on races, but the last couple races of the year aren't typically big goals anyway so I try and maintain. It has worked well for me because it gives me a variety of work to do throughout the entire season. Also gives me that mental break in the middle where I can take some time off to recover then get back into a small build. Typically by the time my 2nd peak hits I feel just as motivated as I did in the beginning of the year. I've had to be willing to accept that I may not be 100% physically for some races, but allows me to relax more. Like my past race I was able to get in a 4 man break, but didn't have the top end to stay with the attacks from the group. Everyone is different and mine has been solely by trial and error and past experience. In college for swimming we used to do 3 peaks and I've taken what I learned about how my body responded to that and applied the same principles to cycling.