1. I think it is better to put down all your clauses, conditions and terms down so that buyers can review the terms and conditions before they buy either the trial or the final version.
FSB Pro Comes with a license agreement. It is available for review during the installation of the program. Actually a user cannot install the program without accepting the License Agreement.
It does sound scary when things are not spelt out clearly and your message is rather tentatively 1 year or 2 years, etc. Doesn't give buyer any confidence.
I do not have any limitations of posting updates to the software. You may check that I'm posting updates to FSB from 8 years. I may do the same for FSB Pro. However I'm not legally obliged to post any updates or upgrades to the software. You may check the license agreements of other products and you'll find the same.
Firstly I thought that the upgrades is free for life
Hmm. What commercial product you are using upgrades for free for ever? Word, Excel, Windows...?
Normally a user buy a particular version.. lets say MS Office 2003. But if a user wants MS Office 2010, he must purchase it separately.
And if the license purchase is valid for life, then upgrades suppose to be free too.
The purchased license is valid for live for the current beta version and for upcoming RC and the final version.
You'll be able to use the purchased software for ever since there is no upper limit neither in the license agreement nor in the software.
3. Lastly, If you decided to charge for future upgrades (and I hope not), will it affect the efficacy of the old version.
This is funny. Are you seriously think, I'll post malicious updated to the older versions in order to make them "laggy and inefficient, or inaccurate etc"? I'll not do it.