No, you should not lose anything, Just do not delete the <.veg> file(s). The project should open again when you re-activate VP-19 with the purchased serial code .. or an upgraded version down the road. The .veg project files are not backward compatible though. VP-18 (or prior) would not be able open a project file created in VP-19.
"You only have one chance of [trialling] each version of each product, though note if you have access to another machine you can install the trial on a new machine." Other methods may be considered as violations of usage rules.
Thank you for all the reply's, I've never done this kind of work before, unfortunately I did not know about the rendering issue until I was finished with my project....ugggg....I'm figuring it out as I go so, I REALLY appreciate your feedback!!
If money is tight, you can always get VEGAS Pro 365 for one month, that only costs $20, that has none of the time restrictions present in the demo. Just be sure to cancel the subscription after buying it if you do not want it to auto-renew. Also make sure that you select the monthly, not annual, subscription. You want VEGAS Pro Edit, it's the cheapest and still contains a full featured copy of VEGAS Pro.