I will do my best to answer your questions. If you purchased iRite 1.x.x (i.e. 1.0.0), you own it and any *upgrades* to iRite 1 are free. Upgrades are considered any time the build number is updated where there are x's are in my example. So 1.0.4 would be free and 1.5.0 would be free and you would own those. As in the past, HTML Editor (which is like a iRite 2.0.0) would cost you an upgrade fee if you wanted to OWN it, which should show up on the Upgrades page under Your Account.
If you are in the subscription program, you are leasing the latest software, meaning now that HTML Editor is out, you are leasing v2.0.0. If there is an upgrade to it (2.0.1 or 2.5.0) or even a new version (3.0.0), you would be leasing those. The benefit is that you can use the latest and greatest for only your monthly or annual leasing cost.
The benefit of owning is of course that you own that license, regardless... but it is true that you must pay a purchase price to own. If we let everyone own the latest for a lease price, customers could cancel their subscription and we'd be essentially giving all of our software away.
In my opinion, the benefit of being a good customer to WebAssist years ago (as you asked, ruffteam) was that you purchased extensions that you have been able to use this entire time, which have hopefully paid off (and then some) in saving you time developing your websites or clients' websites. I guess I am saying that hopefully you have gotten value out of your purchase already. If you want to continue to have WebAssist's latest extensions, you can either continue to subscribe or you can outright purchase licenses.
As far as maintaining sites, the software you own isn't going away. If you have iRite 1.0.0 installed and never want to upgrade to the latest dot release or purchase a new version or subscribe to the extension library, you can still use iRite 1.0.0.
Codamedia, if you own the last version of an extension, you are offered a discount to purchase a new version, regardless of whether you've subscribed in between. If you are really concerned about having the rights to that license, owning may be a better option for you. The cost of leasing is hard to beat... but obviously you have to weigh out what is best for you. Hopefully this gives you enough answers to do so. You can also welcome to call/email Sales if you have further questions.
