I used to own a Blanik L33 solo. I left it tied out. After a while, I seemed to get a lot of water in the static ports and I would have pitot-static failures until I landed and cleared it out. Had pitot blockages too, even though covered. That one was from cutting the grass. How the clippings got that far I'll never know. I would miss the vario but never the airspeed. No way would I do a PTT (premature termination of tow) based upon no airspeed. I think it's a lot safer to sort it out at altitude, especially given our strip is short and ends in a 800' drop off. I gave up on the suction cups I had and took to taping the static ports. Guess what was handy - white tape. Never forgot it though. Now I own a 1-35 and it seems free from water in the pitot static system.
I had the flapper valve that covers the pitot tube freeze shut one time in our C140. It was fine during preflight, in our heated hangar. Water that splashed up from the tires must have gotten it. In the taildraggers I don't usually look inside during the takeoff roll. In the arrow I do especially when playing the IFR game. Since I was aloft and in the easy part of the flight, I thought I would see if it would pop open during the descent and higher airspeed. Never did. After I landed I freed it up. There were no puddles at the airport I flew to, just an inch of snow.
I would say anything that I fly often, I am not overly concerned with an airspeed failure while in VFR. I can pretty much hit the speeds without looking, just by attitudes & power settings. When I fly in the back of a 2-33 I can't see much anyway, especially with somebody big up front. Like any other failure, the number one thing is to fly the airplane, and not do something that makes an inconvenience into a real problem.
-- IFMU