Theoretically, yes, you could extend the life of the boat. The longevity however would depend on several things. If the material is failing apart and the seams are failing it wouldnt be worth it. The material will still continue to fall apart and will be weak and prone to punctures exposing the bladder which is not very abrasion resistant. Failing seams would likely continue to fail to UV and under the pressure of the bladder which would pose the same problem of the bladder hanging out, leading to a puncture. Cost is another prohibitive reason. Bladders are several hundred each so by the time you put a few of them in you would quickly get up to the cost of a decent used boat, which would be a better overall idea. Having to repair seams that kept failing is expensive and once the boat material has degraded to a certain point it just wont hold glue anymore due to the solvents more less disintegrating the material. There are other reasons that it isnt the best idea but no reason to get into them. Bottom line is, if you brought a boat that was ready for the dumpster into my shop and wanted to dump a bunch a cash into it by adding bladders, I would try my best to talk you out of it.
That said, I have installed Aire bladders in non bladder boats before. The customers have been very happy with the results. Typically it is boats that have several baffles blown catastrophically and the owner wanted a back up chamber inside without the cost of fixing multiple baffles to gain one one chamber. Nrs and Sotar have used a similar idea in their catarafts where they built a smaller tube in the big tube as the second chamber. I installed the bladders in newer boats that didn't have seam and material issues. There are some issues with this approach, such as getting a hole in the tube and bladder and the boat becoming a one chamber boat again which is a real risk. Overall I don't think it is the best option but it has worked for some and in certain circumstances it made sense cost wise so I suggested it as an option.