Assuming the lift-the-dot hardware is of good quality--- ie, stainless--- it should last for many years. Some of our canvas uses this hardware and we've had the boat 13 years and Lord knows when the canvas was fitted before we bought it. Some of it was pretty old in 1998 and, much to my amazement, it's still holding up.
The only problems we've ever had with lift-the-dot hardware is on our caprail covers, which we leave on during the winter even though we use the boat year-round. Even though we rinse the boat off after a weekend cruise, and even though it rains 24/7/365 up here, corrosion does get a grip on the posts and snaps. While we have never had a lift-the-dot fastener fail to snap or unsnap, it's obvious that their lives have been shortened, particularly on the forward quarter of the boat where they are often drenched in spray.
We use Vaseline to lube the lift-the-dot hardware and the regular snap hardware on the boat.