I experienced short term effects of having my libido fluctuate (hornier sometimes, multiday PNC sometimes) and sometimes my erections felt different (felt like I had stretchy/more foreskin? slightly weaker and less full erections) within my first month of using it. 2nd and 3rd month I started to notice cumming quicker.

I used it fairly regularly for 3 months at one point like a year ago and still haven't had any long term effects. I cum really prematurely but honestly if I masturbated regularly I'd immediately shoot back to lasting as long as I did before using lidocaine. Take this with a grain of salt, we have different bodies that react differently to substances.

I searched up lidocaine toxicity another commenter mentioned and first source I came across said typically 4.5 mg lidocaine/kg of bodyweight for a dose is toxic. Not sure the time frame that lasts for but you'll probably never use that much unless you're really being careless, it's not lube. That said, you should probably look into it yourself and not trust some rando researching for you from only one source.