One thing I've said before is that for me, there are too many races in the championship. I'd prefer a 10 or 12 race season that allows a bit of suspense to build up and in an ideal world allow the F1 drivers to race elsewhere. It'll never happen, but I think the current season length is a significant factor in the factor in the amount of bad press generated by the lack of competition up front on track. A short uncompetitive season would be over and done with and the additional funds saved through less travelling could be used to allow for a bit of in-season testing to give an increased chance of some competition.
I'd be fine if more F1 drivers were doing Le Mans and they'd also be able to do the Indy 500. The May/June schedule should be something like this:
Spanish GP
Indy 500 qualies / F1 test @ BCN (reserve drivers only), (Or Spanish GP this week with a different driver qualifying for the 500)
Indy 500
Monaco GP
Le Mans test day on Mon/Tue, Austrian GP on the weekend (to avoid a flight to Canada)
Le Mans 24h
Canadian GP
Of course, that's not happening as F1 doesn't want to let the Best Drivers™ to other series' races.
But anyway, I don't think 20 races is too much if they are well-scheduled. Mostly every second week with a month's break in August it'd be fine. Otherwise it's too much unless F1 is your only interest, I guess that's how some people can watch all the 36 NASCAR Sprint Cup races.
My problem is whenever I missed out an race the race is becoming pretty awesome (e.g. Bahrain 2014, Hungary 2011, Montreal 2008, Monaco 2004). Taking account that I will be on an exchange year from september onwards and I still don't know how to watch F1 there, you can expect that all races from Monza onwards will be an blockbuster.
When I was studying in Germany, I had a chance to see the races officially free (with lots of commercial breaks). And for other sports, the Nigerian Streaming Club always helped.
But, the Singapore GP was in my first weekend in Germany, it was the first race weekend in years I paid no attention to F1, during the race I was at the Oktoberfest and probably enjoyed it a lot more. If anything, during that season I learned to watch F1 only when I'm in the mood for it, otherwise I won't be spending my time only for the sake of a habit.