Occasionally I will play doubles in friendly matches where at least one guy is a 4.0 or 4.5ish player. What I notice is that these guys usually have a fast first serve and pretty spinny but still reasonably fast second serve. what I also notice is that these guys will double-fault excessively when I'm playing with them. I'm wondering if this is because its a friendly match and they don't care how they perform, or if they would play this way in a competitive match because you have to go all out on serves against 4.0-4.5 players? One of my pet peeves is excessive double faulting in doubles because it is annoying to the partner and is preventable if you simply do away with your first serve on days that nothing is going in.