I have submitted a paper on applied probability in one of SIAM journals. The paper is under review for 9 months. I asked the editor 1 month ago about it, I was told that one review report has come and they are waiting for the other. Will it be ok if I politely inquire about it now (I have inquired 3 times till now after submission). How frequently I should inquire from now on so that it is not rude. Another question is that, is it the usual time taken for review in SIAM journals?