YES - there is a distinct possibility your lender will check your credit very close to your closing (like the day before even). They do that to make sure you are still employed (not fired or layed off) and to make sure you haven't done anything that has drastically changed your ratios of debt to income.
A few years ago, even after I told my buyer to do nothing until after we closed, I had someone who bought a motorcycle 10 days before closing, then skipped work one too many times and was fired two days before closing. We went and did the final walk-through with the builder, were set to close the next morning at 10am, he never said a word about either thing and I got a call from the lender at 4pm that afternoon saying he wasn't employed and by the way also bought a large purchase that ruined his credit picture. We didn't close.
This is of course a drastic scenario but true.
Although not all lenders check some do and the best thing to do, after being qualified, is:
1) Don't open up any additional credit streams - credit cards, department store charges, etc.
2) Wait until after you've closed to tell you boss you hate him and are going to work for the competition
3) Don't make any purchases that aren't absolutely necessary - like food. You can buy that great sofa for your new house AFTER you own the house.
Good luck and happy house buying.
Trisha Lee REMAX Boone Realty, Columbia, MO
If you are asking the question because you are thinking about making a large purchase on credit, I would wait until after closing.