I know that Bob Pastusek keeps a file on "Limitied Life Items", so I thought I'd add my observations (for what they're worth). As everybody knows, I bought my L-235 kit in 1987 and have been working on it for a long time. Pretty much everything made of rubber has had to be changed out - tires, tubes, hydraulic hoses, gascolator soft-goods, mechanical fuel pump (just bought a new one), and the front crankshaft seal on the engine.  I'm into the brake system and hydraulics now, and have a few observations.

1. I removed and replaced the Nylaflow tubing to my brakes just on general principles; I replaced it with the heavy-wall Nylaflow, which is probably overkill.  The standard-wall tubing I removed seemed completely serviceable to me, though; It was still flexible and no cracking was observed. While I was doing that, an older (than me) Long-EZ builder stopped by and I asked him about the Nylaflow tubing. He is still flying with the original 30 y.o. Nylaflow tubing on his aircraft and has never had a problem. Down near his brake discs, he wrapped the nylon tubing with some kind of heat-insulating material which sounds like a great idea.  During my aborted taxi testing, my right brake disc got so hot that it discolored the paint on the inside of the middle gear door and caused my Nylaflow tubing to "weep" at the brake fitting. You can see a little meniscus of hydraulic fluid on top of the brass fitting in the photo below, and the softened convoluted tubing. The Long-EZ builder used the brass inserts like I did at all compression fittings. We agreed that sunlight will embrittle the nylon tubing, which is why I ran mine in the convoluted tubing. With all the conflicting information on the Nylaflow, I decided that I just didn't want to worry about it and installed Russell motorcycle brake hoses for the last 18" down by the brakes.:




2. The O-rings in the original Rosenhan brake pucks in the above photo seemed completely serviceable after at least 15 years with hydraulic fluid on them, and 30 years since being manufactured. I haven't used them a lot, but there was no deterioration that I could detect and I stretched them like rubber bands and they didn't break - even the one on the right that got so hot. The Buna-N O-rings have a listed shelf life of 15 yrs, if anybody cares.

3. I've had two hydraulic cylinders leak over the years. IMHO, the primary weak point is the shaft seal; On the three that I rebuilt, the little chevron shaft seals were falling apart. The second weakest point (IMHO) is the piston seal which can cause a leak from the high side to the low; I had one of them leak through. All the end-plug O-rings inside seemed completely serviceable after all this time. I'm just guessing here, but I would give the shaft seals a life of 10 years, the piston seal 15 years, and the end-plug seals 20 years.

Hope this helps...