While I can't say it is true for all computers, my Suunto HelO2 can't be taken out of gauge mode for 48 hours after the dive. Pretty much makes it useless for the next dive. Even using two Suuntos can get you into trouble because of all the different varieties of the RGBM algorithm they use. The latest computers use a "fused" RGBM, while the HelO2 uses a "technical" RGBM and the Vyper Air uses a "recreational" RGBM. ARGHH! I am still looking for a reasonably priced backup for my Petrel. All it has to do is run ZHL-16C. Using tables is fine, but you pay a very large penalty in allowable bottom time because no one dives a square profile!