I Agree with you; Why is the 14 days per move the longest time to play online chess games? I'ma very busy man, and sometimes is very difficult to me playing one time per two weeks. I think that it would be a great idea to introduce a longer time control, like 15 days per move or more, if it is possible..
I'm looking forward to reciving an answer 
Kind regards
at certain times of the year I can connect aSunday and one not, with time control 14 days tomove I have difficulty, I would need a time controlfor 15 days moves or more