Experimental evidence reference would be good Perhaps a reference should be added to the value of 10 years The paper given K Hagiwara et al Particle Data Group current best estimates of proton lifetime Phys Rev D 66 010001 2002 ISBN 978 06848657680 dates from 2002 and is presumably from the 2001 Super Kamiokande results You will be aware that the average non specialist reader will have seen 10 years or just 10 33 years and this is the value that other google sources bring up from the same Super Kamiokande experiment e g the hyperphysics phy astr gsu edu site As of 2001 it seems that the proton lifetime has been pushed out to at least 10 33 years which point Isn t 10 33 strictly equal to 10