from what ive read, which is a lot since mc!!
an egg lasts 12-24 hours so try and use ewcm as an indication too.
spermies last up to 5 days (max)
Im not sure about positive opks but i think i got + for 3 days but had very little ewcm so unsure if i actually ovd, which is a problem with these. It can show you your lh surge but not if you actually popped one out. (only used them last cycle so not 100% sure on that one)
if you could fit a quickie in on wed maybe just to be on the safe side?
Anyone, please correct me if im wrong :)