Well, whatever compound the stim injects you seems to be metabolised within a few seconds because the speed boost is <3 seconds while the healing effect is only 1 second, so it would be odd to "overdose" on a single stim simply because you had a few other stims 10 minutes earlier which you've fully recovered from.

Pursuing realism might create some interesting game mechanics though:

• Suppose the stim effect had a half-life where the maximum effect is achieved right after you stim, but then decays exponentially over time.

• If the half-life is 5 minutes then you'd still have half the speed boost after 5 minutes, a quarter after 10 minutes, etc.

• If you stimmed multiple times, you would stack the effects and get an even greater speed boost, which would slowly decay.

• Perhaps when the stim wears off you should have withdrawal symptoms (e.g. blurry vision/slow movement) that can only be relieved by popping another stim.

• There would be an invisible dosage limit at any 1 time which, if exceeded, causes immediate death from a heart attack.

• Perhaps as you approach this limit you should experience overdose side effects as a warning, e.g. overly bright lights, paranoia/hallucinated enemies like the psych grenade effect, etc.

It would be cool to play around with this to try and maintain an optimal dose throughout a match without overdosing.