Take a look at this post to get a little more background and to see a UIM sleeve procedure inspired by the KenCo company who pioneered the sleeve and reduced diameter pipe fix several years ago.
Long-term test results for stainless steel UIM sleeves are not available yet. No one (at least that we know about) has installed stainless steel sleeves for much more than 6 months. Bob D. just went a more elegant way by using adjustable reamers to more accurately cut away the damaged and excess plastic to provide room to install a 7/8" ss sleeve.
I have only put about 8000 miles on my sleeved and re-piped intake. The "standard fix" is to replace the UIM and not do anything with the stovepipe or sleeve. The replacement UIMs are supposed to be strengthened in critical areas making them less prone to failure. A standard fix should go at least as long as some of the less robust originals, - say 60,000 miles. For most guys, that'* good enough, and they don't care to install a smaller pipe (as GM did in '99) or to sleeve the upper in an attempt to provide a more permanent fix.
The other problem is that even if you fix the upper permanently, the jury is still out on the longevity of the lower intake manifold gaskets, which are also known to fail.
Those of us who don't ever want to see an intake manifold failure again and who don't want to spend a lot of money have chosen to sleeve the upper, install a reduced diameter pipe, flush and change coolant periodically, install new design lower intake gaskets, and 180* thermostats.
Others are working on adapting the new series III metal UIM to the series II, but have not as yet posted here about current availability.