Tendonitis or tendonosis?
Apparently there is a difference. I have fought with it intermittently over my later climbing career, but have been doing the twisty arm stretch as per the article below whenever I feel it flaring up, and it seems to bring it back under control. Like any chronic injury though, you probably have a lot of scar tissue?
http://www.athlon.com.au/articles.htm
see - dodgy elbows article.
PS usual disclaimers apply - I know squat about medicine etc.
As a long term sufferer of Tendonitis (nearly 10 years now), I have picked up a few things over the years, the above advice on this site, and various articles are excellent.
In addition to this, here is what I have personally tried over the years that has worked for me:
Hot/Cold Ice treatment: Excellent but needs to be done 1-2 times a day at least to see the benefit and for long periods of time, Sauna to Ice cold shower/plunge pool seems to work a treat as well.
Deep tissue massage, painful but makes a huge difference, 1-2 a month for a while and I felt pretty much perfect for ages, but it is expensive to do this for a number of months, would do it all the time if I could afford it!
Steer clear of fingerboards!
Use other devices to train your grip in various ways, I was doing 1-2 sessions a week for a couple of months indoors with no problems, 1 finger-board session the other night has put me out for a week, and it didn't even feel like I was trying that hard!
Regular self massage, avoid tricep exercises that put the joint in risky positions where there is a high chance of injury: such as overhead tricep extensions, one of the worst exercises for injuring your elbows, steer clear of these or anything similar, also avoid tricep exercises where the wrist has to twist much.
Swimming, absolutely awesome, I like to switch up between front crawl, back crawl, and breast stroke, great for recovery/strengthening of the elbow when its feeling a bit fucked, and very complimentary to my bouldering I have found

Oh then there is the shitty last resort: Hydro Cortisone injections, which can help if they get really bad, had them and they did the trick, don't think I would resort to that route again though, as it means a lot of time off recovering to get the best results.
My two pence ^
Hope that was useful
