If a person didn’t say Asher Yatzar after using the bathroom, and by the time he remembers he needs to go again to the bathroom but he won’t be using the bathroom for another while(because he’s at work etc.)and he feels that he can wait 72 minutes, and if he would be distracted he would probably forget that he needs to use the bathroom, so should he just say now Asher Yatzar for the earlier time that he forgot to say? If he shouldn’t say now Asher Yatzar, would it be ok if he says brachos and eats in the meantime?
After using the bathroom we may say asher yotzar only until the feel like using the bathroom again, even if we can wait and don’t have to use it now. This is similar to making a bracha achrona, that we are allowed to say it until we would want to eat again, because then it is considered that the original pleasure is finished, since now he has the need again.
Regarding making brachos when one has a need. A person that needs to use the bathroom, (and it doesn’t just go away by thinking about something else) should not make brachos, even if they would be able to wait 72 minutes. B’dieved, if he made a bracha, he does not have to say it again, since his need is not so great. If however it is a type of brach that if he will wait until he gets a bathroom he won’t be able to say the bracha, i.e. on thunder, or tefilas haderech, then he is allowed to say that bracha now, since he can wait 72 minutes.
M:B 7-1, Mor Uktzia O:CH 7. O:CH 92-1, M:B ibid 6, Piskei Teshuvos 92-4.Eshel Avrohom (Butsatch) 3-3.