Newfie, it certainly is a personal choice, but if you're not having the 21 day progesterone done each month, it's hard to know if the specific dose of Clomid you used earlier is still working. Sometimes what works one month, fails you the next, particularly with these medications. Charting would indicate and further confirm ovulation after you see a distinct temp rise after your "O" day...and OPK's give you a heads up that you're not missing the mark bd-wise, and timing intercourse poorly.
Really, you may as well maximize your medicated cycles, and at least begin using OPK's, 3 days after your last Clomid pill. This will tell you when to start bding, and if you get a LH surge, which is a good indication that you're about to ovulate.
I'm sure none of it is mandatory, but I know with my OB/gyn, she really likes to know what's happening with my cycles, with as much detail as possible.