My 2011 MacBook Pro is doing a lot better than my 2007 one. With similar use, the older MacBook went through about a battery every year and a half, replacing on

My 2011 MacBook Pro is doing a lot better than my 2007 one. With similar use, the older MacBook went through about a battery every year and a half, replacing once they could only hold up an hour or so of charge. I'm up to 750 cycles and holding high at 98% "health". The OPs MacBook air sounds defective, or at least, under-performing.