A customer buys a $300 hosting account and then that account is good for life. You get NO money ever again, yet you still have to support every client like they were new.
If you don't want that as a company, DON'T offer lifetime licenses without yearly support pay in the first place.
Some company's start with a good idea, give something for free.. Other company's follow, don't think about it, and after a couple of years they start wining that they don't make money anymore.
Well, think about that before you start copying other company's then or starting to do "unlimited lifetime" things. It's not fair blaming the customer that they want everything for free if it's offered to them that way, that's not a nice attitude.
If you offer it for free, except the consequences or don't sell it that way.
I got mad when vBulletin changed their license stuff. I got a lifetime license and as a customer in that case I may expect that things stay the same for me as long as I use it and I can upgrade the way I always did.
Now to get new versions, you have to pay a complete new amount to get a new version, for something people should only pay support as is agreed in the buying agreement. So I stop at vb 3.8 with 3 forums, they won't get any penny from me anymore, and all best people went away anyway when vB was taken over so... It's a pity.
So I agree with scsi here.
However, I also understand your point. And since Directadmin has great service, I would not mind if there would be a kind of payment construction in the future. Like keep the forum support for free and the updates, but charge f.e. $ 20,- a year for personal support by email (except changing license ip's). And maybe charge $ 10,- transfer fee if you sell your lifetime license to somebody else, free transfers all year when you payed the $ 20,- support fee.
I don't think customers would see that as a problem if it was done like this.
But don't start an obligated yearly fee. I hate that too.