Take comfort in using the Derby for an extended period of time; you really had no choice. Even had you found a shop with shaving supplies after three days at Disneyland you wouldn't have been able to afford a single blade anymore. Lol!So i found myself in Disneyland Paris for 3 days recently, upon arrival i realised I had brought everything except spare blades. In my razor i had a Derby blade used once ( not my usual, that's Astra). Given that i was tied up from dawn until dusk i had little choice but to use this blade for the duration. Usually i always toss a blade after 2 days as i have moderately heavy growth assuming that its done however to my surprise I managed 4 days close shave (4 passes) without irritation or noticeable degradation of shave quality. So this got me thinking, how long does a blade usually last? Does the mildness/aggressiveness or brand affect this? I appreciate this might be subjective but I'm thinking if anyone has tested this its likely here.