As far as I know, you can spray as much as you like freely, I do!
However, never, EVER unscrew the top and pour it in your pan. This way is definitely synned, as you'd obviously be using much, much more than spraying alone.
Until your finger hurts? Wow that's a fair bit. I never use more than about three squirts in what must be a 10" pan. I do find heating the frylight then cooking over a much lower heat def is the way to go. Took a bit of getting used to using it but even hubby fries in it now.
I'm on my second bottle since I started! If I'm frying an egg or making an omelette, I usually go for 4 sprays in an 8 inch pan... With SW chips, I go for gold! Today, I didn't want to use any syns on margarine on my toast, so I sprayed Frylight on it and stuck it with the sprayed side down in the frying pan after I took my egg out, lol! xxx