I'd go with what the laser centre tells you. You don't mention that the centre told you the Emla must be anerobic to work. That is, you need to block out the air after you put it on, and it needs to set for about 20 minutes to be really effective.
I used it for a while prior to electro., but got tired of leaving home and driving to my appointment with a piece of plastic (Saran) wrap stretched across my face for the 20 drive to my treatment. I used to poke a hole through it for my mouth, being careful not to uncover my upper lip. Also, if the receptionist said there'd be a few minutes wait, I'd end up sittig the the lobby wrappped in plastic wrap for all to stare at. If the centre does it for you, I think you'll be guaranteed the 20-30 minute sit in the lobby while the stuff kicked in.
Once exposed to air the Emla begins losing effectiveness fairly quickly, so it would be no help after the first 30-45 minutes of a 1 or 2 hours appointment. Quickly I decided it was a PITA that totally outweighed the benefits. I hiked up my big girl panties and took it like a woman without medication.
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Diana
Sticks and stones may break your bones, but words will break you heart.
Anything essential is invisible to the eyes.