My partner and I have a not-quite-2-year common law relationship, and we sent a word document with a history of our relationship from day 1 until our app was filed with photos of any and every event we had photos of. I think there were somewhere between 60-70. I'm not anticipating any problems, but I wouldn't say that photos are even half of our proof of genuine relationship. For us, emails, skype history, phone records, letters/cards to each other and support letters from friends and family are more of the bulk. I have also heard on this forum of people who have been married for years and years and only sent 10-20 photos and were approved no problem. I really think it is individual to the situation and if you have a strong case overall, you should have no problems.