I've been ignoring this issue since I started getting the nag screens a couple of years, but I'm in the same boat. I've been using CCleaner since I was an email administrator in the early '2000s, and bought the pro version in 2013 for the extra little features. I've still got my confirmation email and there is no mention of a time period except for the download link, which would have expired in about 60 days for some reason. Most of the features it offers can be done with built-in Windows disk management options, but the convenience of being able to schedule things in the background was nice, which is what the Pro Version allowed me to do for years. As a comparison, I bought the pro version of Malwarebytes around the same time, before it went to a subscription service, and they've always honored my lifetime license.