I think you can get into semantics over a wide variety of definitions as to what a lifetime roof really means. Here’s some things to think about and perhaps it creates more questions then it answers but, here goes. First, everything seemingly has to wear out at some point in time, even a metal roof loses it’s protective coating after a while. Increasingly popular Presidential style material comes in single (30 year life), double (40 year life) and triple (50 year life span). I have no doubt that even the triple thickness material will wear out eventually depending upon the conditions around it. These high quality roofs come with algae blockers built in but, that’s really only a guarantee for maybe the first 5-7 years. If someone doesn’t start treating every other year after that I’m sure the moss will take over and create adverse conditions thus, shortening the lifespan.
The manufacturers ‘lifetime’ warranty is going to be subject to certain conditions, you can almost bet. For example but not limited to, it may or may not be transferable. Looking a bit deeper into possibilities, in order to protect themselves from every having to replace a 50 year old roof there are certain maintenance items that must have been adhered to & documented along the way. Examples might be you could have some responsibility for not allowing it to grow a coat of moss or maybe they say it must be installed under workmanship standards that exist currently. In regards to the latter, requirements for venting and installation are almost constantly changing for the better. It wasn’t that long ago that you started seeing typical metal roof vents that allowed a roof to ‘breath’ being replaced with a single long ridge vent that looks almost like they forgot to fasten down those shingles along the ridge. Of course every manufacturers ‘lifetime’ warranty may be structured to suit their own needs so the possibilities could be endless.
The reason I mention all those things is very few people ever get to the point where they recall they have such material on their roofs, see it on packaging left over from a previous owner or perhaps more importantly have read all the fine print and can document the ‘life’ of the roof. Another factor is whether that manufacturer is still in business ? It also may be that if they are in business, a roofer can get some reimbursement from the manufacturer. It’s also possible that replacing with the same material no longer makes sense or the improvements are so vast that seeking out ‘old’ styles may not be practical. Roofing material is constantly changing therefore it could be that manufacturers know full well that having to ever replace material they sold 20 + years ago is very slight.
Part of the equation in getting a reimbursement for so called ‘lifetime’ roofing will hinge on whether it was installed to their specifications originally. Having the very best Roofing Contractor install your roof is critical to preserving any claim you may have in the future. Of course, in addition to a warranty on materials from the manufacturer there is a warranty for the much larger part of the job, the labor to install your roof. In some cases your looking at just several months to perhaps a lifetime so, that becomes more important with that cost being maybe 2/3 of the overall expense of replacing your roof. We can’t predict who & who won’t be around a long time from now but, certainly selecting a Roofing Contractor who has the best track record for installations and will hopefully be in business decades from now are considerations.