EA Access does it best.
Currently playing 10 hour trials for both Star Wars Battlefront and Need For Speed.
I really like Battlefront and will certainly buy it. Need For Speed on the other hand is not worthy of a full price pruchase IMO but enjoyable enough to finish the trial and you can achieve a lot in 10 hours.
On the other hand if all games had such a trial, I probably wouldn't buy anything 
2-3 hour trials should be long enough, but I'm not complaining 







