If twenty minutes is not enough time, just restart the program, as you've already discovered. The inconvenience of a restart is not relevant. You will either like the product or not. That all the demo is meant for.
20 minutes is not enough time. When each 20 minute cycle ended, and I was in the middle of playing something and the virtual piano went silent, my first thought was that something was wrong. Eventually I would remember that I only had 20 minutes to work with. What a lousy way to market piano sample software. From a performance and evaluation perspective, it kept dying every 20 minutes.
Anyway, what is the alternative? An unlimited demo? That's not a demo at all. That's a giveaway.
As for the disabled notes ...
But what's worse is they deliberately disabled some of the notes in the demo version. So I'm playing music and stumbling along in the evaluation because notes AREN'T THERE to be played or heard.
Once again, what is the alternative? If the demo included all notes, what would be the incentive to buy the product!
Anyone could simply use the demo!
So it's clear that the demo must have some kind of severe limitation, such as disabled notes. Otherwise a clever person could simply defeat the timeout and be done with it.
To defeat the timeout, I can think of two ways (and there likely are more). Here's one ...
This clever person could arrange for a second copy of Pianoteq to run, starting at a different time from the first. The first copy would listen to one "pseudo-MIDI device" such as MIDI Yoke. The second would listen on a second MIDI Yoke port.
He'd write a special hack program that reads data from the "real" MIDI port, and forward it ONLY to the first MIDI Yoke port. Only the first Pianoteq program would play. The other copy (listening on the second MIDI Yoke port) would remain silent.
Then when the first-run copy of Pianoteq approached its twenty-minute timeout, the hack program would cease sending data to the first port, and send instead to the second port. The second copy of Pianoteq would play, and the first would go silent. Then the hack would kill off the first copy and start another one, again listening on port 1. That one would remain silent. Only the second copy would play.
This could repeat forever, shuttling back and forth between two copies of the demo. No purchase necessary.
To me, this is way too much trouble. (Fun to think about, but not worth the effort. The darn program only costs $100.)
But what seems too much to me might seem a modest programming exercise for an enterprising youth. He might offer the hack for free, and this would put Pianoteq out of business. (OK, not really likely. It's more likely that Modart would simply stop offering the demo version ... or they'd do just what they do now: offer a timed-out demo with some disabled notes!)
But don't fret. The demo versions from other
piano makers allow you to play precisely ZERO notes. No demo at all.
I think that a limited demo is better than no demo.