hmmm...for me depends:-

1) if the uneven road is just small patches.....just continue driving at the speed and find the best possible line through it

2) if there is large potholes, either avoid it totally or slow down and drive through very slow (20kmh).....slow down meaning hitting the brake at very early stage and not hitting the brake like emergency......this is to avoid accidents ......

3) i will never increase my speed over uneven road unless i am in a hurry/emergency.....

funny formula.. but i like it... 

i understand what you mean but you have overlooked one part, which is the threshold of the rims, tyres, alignment and absorbers/spring.

the formula makes sense.  but your explanation lacks a little. Though T decreases with speed, but S increases with speed.  The thing here that you are missing is how much T decreases and how much S increases.

In my humble opinion,

Say you increase speed, T will decrease linearly but S will increase exponentially making H very high.  Since T will never be 0(zero) there is no way H will ever be low.  This means that there will always be significant amount of H(hurt) to your car at high speed.

Say you decrease speed, T will increase and S will decrease. Say you reduce your speed to about 30-40km/h, you might be ablt to decrease the S to almost 0(zero) where you do not feel much impact to your car as most of the uneveness is absorb by the car tyres, spring and absorbers.  This means that H will be almost 0 since S is almost 0 

he he he......so......just drive how you see fit.......experience tells me that driving fast through uneven road means changing absorber faster!!!!

you can always drive faster if you are confident of your car but never ever drive fast past potholes.......