In reply to Kemics:
I get the logic you started with. Mates loose weight and grade improves, you dont feel you can, so logically look at building power endurance.
I suspect looking at your replies theres a number of suggestions, my first is that the two times you climb per week are looking like 'social climbing', not a bad thing, but I fell into this trap, chatted with mates, did some climbs, tried some, fell off some, had a laugh but didnt really improve.
I broke the cycle by writting a training plan and sticking to it. Writing down a 12 week plan. Core work/approach to my wall sessions/upping the quantity and the quality/fingerboard sessions did it for me. When I returned to the social climbing I saw relative improvements and was climbing harder than friends.
Perhaps this is you main weakness, mentally you need to break this cycle of social climbing, a new venue might help or a shift into a training mentality might be the key. Only you will know.
Next I want to do something similar, increase power endurance so I'll watch this thread with interest. For me continuing the above, doing a bit of lopez weight sets plus 4x4's is the vague notion.
Post edited at 13:15