First, are there any good threads about time between cycles, # of cycles ran etc? I was not able to find what I was looking for.

As most start I am just starting to dable in AAS and was hoping to do a cycle or 2 to help build some mass, then continue a proper diet/workout program to maintain most (hopefully) of the gains. The more I read the less likely I think this is going happen. I started around 170lb 5-9 at about 13% body fat which I feel like I have been at forever. I'm 3 weeks into my first cycle (test/dbo/nolval) and its going great. My questions are:

My original plan was to run 2 12 week cycles to help add 20lb of mass which I believe my frame can maintain just fine. What should be my time between cycles and future cycles if I decide to do so. Am I wasting my time planning on just running 2 cyles or should I be able to keep a good portion of my gain with proper pct and training?

Also my supplier ran out of test eth and supplied with test cyp for the last 4 weeks of my 12 week cycle. Is this going to be ok or should I end the cycle at 8 weeks?