In reply to purplemonkeyelephant:
At the risk of sounding daft...
I had a similar issue (was only climbing indoors once a week, and not making as big improvements as I'd hoped for - was also feeling that I was getting pumped more quickly than I should've). I noticed that on the way home I'd pass a number of trees, and one day decided to climb one, do pullups, etc. I now try and do this every evening for 5-10 minutes, and have got marked improvements in my climbing ability. As the branches are so wide, it really does not stress the joints and is kind of like holding a huge sloper.
Have also got a weird tree in the backyard with a big "crack" in it which is perfect to practice laybacking, and a nice high branch that I've practiced prusiking up / abseiling down (with a rope slung over and suitably tied).
If I was back in NZ, I might even practice my front-pointing going up the big shitty pines in the backyard too
In short - trees have improved my climbing ability, and are free.
Also got 2 captains of crush grippers that I keep on my work desk and do a set of 5 every now and again. Mostly helps with general hand / forearm strength.