I would expect the tolerance build up to negate the positive effects fairly quickly. Most people that need to have their coffee in the morning are NOT more awake than a non-coffee drinker but need the coffee to just reach their normal baseline.
So you would need higher and higher dosages to see any positive effects and at that point you get nasty side-effects like heart racing and insomnia.
People develop tolerance at different rates, and it depends on dose and usage pattern, etc. It's not hard to use caffeine a lot and never develop a strong tolerance. (Probably not true for everyone, And it's a different story if you've already been drinking multiple cups of coffee every day for decades).
There's some really fascinating research on caffeine use out there, highly recommend that rabbit hole for the interested.
> nasty side-effects like heart racing and insomnia
I've been drinking coffee daily for two decades now and haven't ever experienced heart racing, nor insomnia if I limit my consumption to the A.M.
People do process caffeine wildly differently through. I apparently have genes that make me not very sensitive to caffeine at all, but I know this isn't true for everyone.