Neil RX

Hi, i have just joined the forum and on the look out for a 2003 - 2005 RX300 SE-L. I've been trawling through the search pages but couldnt find anything on the expected life of air suspension. I know its fairly dependent on how it has been treated but what are we talking 20, 40, 60, 80, 100k life? It would be nice to know if i should set 3-4k aside for parts and labour! May well consider a well specced SE with NAV / parking camera as an alternative. Thanks Neil