Usually when we are having intercourse the penis gets harder and harder. If you desensitize the penis, this won't happen, you just stay half soft. And half soft penis is more likely to come to fast.
Your Partner Will Also Suffer
You of course a least partly trying to work on your problem to be able to satisfy her. Well the premature ejaculation spray / cream will desensitize her just as much as you, no matter what the manufactures says. This will make it almost impossible for her to reach orgasm no matter how long you stay in there.
The only way to avoid desensitizing your partner would be to wear condom over your creamy penis. But I am telling you this kind of sex will not be fun.
There Are Endless Better Solutions
If premature ejaculation creams and sprays where the only premature ejaculation solution available I might suggest that you used it once in a while.
But there are so many other ways, better permanent solutions that will indeed cure your premature ejaculation not just give you sad relive once in a while, that I suggest you go for some of them.
The best way is to practice premature ejaculation exercises.
Hypnosis for premature ejaculation is also very good