I have had very good luck using CRC Power Lube available at Napa Auto Parts on my Shimano STI levers.

I had one 7sp rear lever rebuilt by Jim McVey, and it works great now. All of the others that have become stuck or stopped working I have sprayed into the internals with the CRC Power Lube, and after a day or two they started working again and continue working.

I think the main issue with most of the older Shimano STI levers was the grease/lube they used turned gummy as they aged (combined with making them virtually non-serviceable).

OP: when you say 10 speed is more durable, do you mean just DA, or also Ultegra? Just curious as I have some of each (9 spd DA, 10 spd ultegra). The oldest DA shifters aren't crisp but don't miss their shifts. So it's probably just the lube getting gummy. I'm wondering if the 10 speed stuff will eventually start feeling the same way.

IF I ever attempt it, it will be in a sealed glass case with integrated gloves so you can work on the shifter without unsealing the glass.

BL

The newest 10s stuff is a very different design than the 9s and 1st gen 10s. I have seen quite a few ultegra 6700 with snaped brake levers from crashes, so I would vote the first gen 10s are a little more durable in that respect. I would assume 10s would also start feeling the same effects of age 10-15 years down the line. Shimano still uses that neon green grease on everything... looks like grease snot, and the consistency reminds me of the old Johnny Snot grease from grip shift.

As far as getting out the older shifter gummies, I have had positive results with some shifters soaking them in lube (or ultrasonic heated parts washer) to get them working again... usually it is with 8s shifters that they come back good as new. The 9s seem to usually be just worn out.

I have never had trouble getting them back together (haven't tried yet w/ 10s), it has always just bothered me as to why they don't work... sometimes I just can't see an obvious reason unless something is broken. If this shifter actually works it will be a first for me having one repaired other than having the gummies taken out, i'll keep my fingers crossed.

IME, lotsa of 7700/6500 had 'issues'. Primarily, the big lever would 'travel' with the small lever when trying to shift to a higher(smaller cog) gear. Holding the big lever out made the shift possible. Flushing helped many times but many times it did not. shimano changed the shift mech to mirror the XTR/XT shift guts when they went to 10s and these were, IME, much more reliable(altho the 7800/6600 seems to eat der cables). I have seen few 7800/6600 and NO 7900/6700/5700 fail to date.