I know how much mortgage apps have changed..we went through refi April 2010 from 5.75 to 4.75 cost $2800, they asked for stuff I would never imagine, tax records, bank statements, stuff that in the past was only for FHA loans where people were putting down 0-3%....now everybody gets the microscope treatment even with great credit and 20%+ downpayment.
My wife and I waited till afterwards to get card offers....then we find out last month she is getting transferred to DFW and we have to buy new house out there next spring/summer. I will have no job when we get there and she will qualify us by herself. I will continue to slowly get cards, but she won't sign up for any. I also will cancel a few un-needed business cards for her now and hope the effects will drop off (I would think 6+ months would be time enough)
If it were 3 months or less I wouldn't risk the hit. She even got AA to give her statement credit so it will stay open. we cancelled 3 out of 4 SPG cards, keeping her personal one open (must remember to put my points in her account).
I think the main things considered in todays loans are scores over 740 or 760 depending on who you talk to (shopping rates on bankrate.com and through brokers)...low debt to earnings ratio, low credit card utilization...(the number of cards shouldnt matter unless it's extreme and mostly new), the size of the downpayment and the loan. A mortgage broker can tell you what his lenders look at, ask yours what to do, he will most likely have the same advise as many here...do nothing unless you have too many accounts open.