Both in Happ with xray-core 25.9 and V2BOX with xray-core 25.7 in iOS 18.7, I noticed that the memory used was gradually increasing from around 12M initially to finally 50M and made the app crash.
It took about from less than one hour to several hours for the final crash to occur.
If any further info about this topic is needed, I will provide as far as I can.