Re: 20+ years of slow running hot water
Make sure all the supply valves are all open fully (at the street main, the house main, the hot water heater or boiler or both, all of the sink angle stops, etc). If the problem is in one or two fixtures and no where else, then it's probably an obstruction within the valve. If the water heater has been replaced, then sediments and debris could have been dislodged within the piping and is now blocking the valves, requiring the valves be taken apart and cleaned.
Clean all your aerators and shower heads. Even though your cold pressure is fine, aerators do collect debris and will reduce the pressure.
I suffer from CDO ... Its like OCD, but in alphabetical order, LIKE IT SHOULD BE!!!