Paint strainer removal

Im about to start using my paint strainer hop bag which will hang into the kettle. Under normal circumstances the hops stay in contact with the wort untill racking to the fermenter. The problem is I can't put the lid on my kettle while the hop strainer is being used. I could leave the lid off but Im concerned about infection. I am particularly concerned about flame out additons. How long do they need to be in contact with the wort for ?
Or - at what temperature during cooling (with I/C) can I remove the hop bag without having a negative effect on the beer ?

I personally wouldn't worry about using the lid. From flame out to racking for me is about 20 minutes give or take. My lid is off the whole time for that process and I never had an infection on the 30 some brews I've done. As far as how long the flameout hops need to be in the wort to be beneficial, i have not a clue! I would think 5 minutes or so would be fine, but don't hold me to it. Cheers!
tom

I have a mesh bucket straining bag with an elastic top that I keep in my bucket of Star-San. If the brew kettle is going to be uncovered for any length of time (e.g. between flame-out and racking), I simply wring out the excess sanitizer and stretch it over the top of the kettle.

I suppose a paint strainer bag would work also, but my strainer (purchased at the LHBS) is very shallow - not really a bag at all.

-Steve

I have a converted keg for a boil kettle, so I don't even HAVE a lid. Unless you live in a filthy place where dust, dirt, bugs, molds, etc are going to dive in your kettle when the wort is between 120 degrees and pitching temperature, I wouldn't give it a thought.

I brew outside in Arizona, tons of dust and dirt can blow up in a moments notice, I have no lid for my keggle and to date no problems have cropped up. Although here I do have to plan for the weather so my wort doesnt turn to mud. If you get dust storms like we do, just try to plan a brew around it!

Just a pic of one of our dust storms cropping up:

Thanks all