THANK YOU! As somebody who has been building websites since 1995, I truly appreciate companies like yours who do worthwhile upgrades/updates, and offer the updates without cost, particularly on an extremely affordable $20 piece of software.
I think your policy should be for those who lose their download link, they should simply buy a new one. The $20 cost is less than the time you should be spending educating people on how to manage their digital assets.
TIP for newbies: generally it's a good idea to keep back-ups of your websites ... if you're building a sitemap with a product like this, you should be saving copies of your entire website to your hard drive, then saving that to a second drive optical media, flash media, or similar. When you BUY software like this, you should be saving it to a "work" folder in the same place as your site backups, and you should save a copy of your receipts, logins, etc in the same folder as the cgi/php or other scripts you buy.
Remember it's not this company's fault if you can't keep track of your digital assets. Please be kinder in your comments for these folks, as they are invested in doing good software and not managing your email.