As did many others who replied here, we started out tenting and then had a couple of pop-ups. When our son was in college we took a hiatus from RVing knowing that it was our retirement goal to buy an RV.
When we retired in 2005 we took the plunge. After looking at Class Bs and Cs we found that we were much more comfortable in a used Class A. We took an 8,000 mile trip around the country, and the only change we made afterward was trading up to a slightly larger (used) Class A with slides. We almost certainly will not be able to afford to upgrade again. Quite honestly we couldn't afford the last upgrade. The rig we paid $80,000 for is now worth perhaps $40,000 5 years later. But we wouldn't trade a minute of all our experiences to get our money back. A trip around the country, two trips (as Trekmasters) to Alaska, two summers workamping, and lots of smaller trips in the middle. It's a great way to live.
When we leave this earth we may be broke, but we'll go with a smile on our face!