I'm not claustrophobic and I'm very lazy. I'd do it. I got pretty annoyed when I tried a "sensory deprivation tank" and there was light and sound leaking in. 48 hours is a long time, but not dangerously so.

https://en.wikipedia.org/wiki/Sensory_deprivation

In chamber REST, the subject lies on a bed in a completely dark and sound-reducing (on average, 80 dB) room for up to 24 hours. Their movement is restricted by the experimental instructions, but not by any mechanical restraints. Food, drink, and toilet facilities are provided in the room and are at the discretion of the tester, who can communicate with the participants using an open intercom. Subjects are allowed to leave the room before the 24 hours are complete; however, fewer than 10% actually do because they find the chamber so relaxing.[8] Chamber REST affects psychological functioning (thinking, perception, memory, motivation, and mood) and psychophysiological processes.

Those people were allowed to eat, drink and eliminate (and presumably get up and stretch while they did), but this doesn't seem terribly far off from your question.