I have found that if i inflate my cheep LBS tubes to 90 psi, they will be at 80 by the end of the day, but lucky for me.. they will hold 80 for 2 weeks straight and so far, I have not seen it drop below 80 at all !
WOOT !
now, on my wallysmart huffy, i had to top off the tube every single day... glad those days are over !!!!!! ( not for the refilling, but for the huffy ! )