Haven't read all of the responses to this original question but, obviously, the answer(s) is one of those "it depends" kinda things. Everything heilbron alludes to, and then some, is important: not the least of which is proper care and maintenance of the cartridge stylus and consistent use of something like a good quality carbon fiber record brush. Where the stylus meets the groove is where the magic happens. So, it's critical to take good care of these two components and keep the stylus clean. Use of something like an Onzow type cleaner, a liquid type cleaner or something more high-tech before and after every play of every record side is very helpful. Some recommend use and proper application of a liquid stylus cleaner occasionally, even when using an Onzow type stylus cleaner. Some recommend use of a stylus treatment like "Last Stylus Treatment", as well. Use of "Last Record Preservative" after records have been properly cleaned, including new records, is also helpful. Yes; new records should be cleaned before playing them in order to remove mold release agents and other residues left from the record pressing process.
Obviously, 50 and 60 years ago, the technology we have now did not exist. At best, audiophiles back then used things like the Watts Disc Preener and the Discwasher with D3 or D4 solution. The records I have from back then still sound great and they have been played a ton. They sound better still, after an ultrasonic cleaning and treatment with Last Record Preservative. My entire collection is stored properly and every record I have is stored in high quality antistatic sleeves (e.g. Mofi's Original Master Sleeves) inserted into the record jackets with the sleeve opening to the inside of the jacket; not facing outward. I also use high quality outer sleeves, as well, but those are mainly to protect the jackets.
The fact of the matter is, even if you only did a few of these things or none of these things, as long as you didn't go out of your way to abuse your records they would still last a very long time. However, sound performance is the audiophile's holy grail. I have records from the 30s & 40s that I inherited from my parents. I wouldn't dare play them on my turntable without cleaning them, first. I'm sure they will still sound, at least OK. The records I bought in the early 60s, 70s, 80s, etc. still sound very good and sound even better (i.e. excellent) after a good ultrasonic cleaning and treatment with Last Record Preservative. This is largely because I have always taken good care of my records. Some sound better than others, of course, but this is a factor of the sound engineering at the time and the quality of the record pressing process. As one commenter put it, if you take good care of your records they will outlast you and continue to sound great. The wear that happens at point of contact between the stylus and the grooves is miniscule. If you take good care of your records they will outlast you and your children, so long as your children take good care of them, as well.