Dennis Cieri did negatives. 500lb+ bencher at 198 raw for years and years.
Some guys use them. If it helps, do them.
Personally, if you have a 4 post rack, set up the safety bars and do some very heavy negative singles @ max or above. Cieri always did very light weight for a multiple second count of multiple reps, but I think multiple reps would get you very sore quickly.
Learning to lower heavy weight and placing it correctly on the chest is just as important as the press itself. It'll teach you to stay tight while lowering the bar under control.
As for frequency and programming - depends on your programming but I'd keep them on the max effort days or heavy days and maybe once or twice per month for 1-3 singles.