If you are planning to leave Any bike unattended for ten hours, please keep in mind that Any lock or chain can be defeated in under three minutes. if a thief has the tools needed to defeat anything above the most basic lock and chain, s/he can cut through or break Any lock or chain.

Basically, if the thief has a hacksaw, it might take ten hours to saw though a lock or chain ... but if said thief has an angle grinder or some 4-foot bolt cutters, in ten minutes your bike will be on its way to a new home.

For me the question would be, how bad is bike theft in the neighborhood, and what type of thieves? If most of the theft is casual---bikes locked with cables which can be cut in under a minute with a pair of pocket-sized dikes---then a serious chain is enough. if there are serious professional bike thieves using serious tools--the kind of stuff you cannot casually carry down the street in broad daylight---then don't lock your bike there.

Particularly if it is a regular thing---if your bike will be in the same place for a long time every working day during work or class hours, then someone will eventually figure .... two locks and chains would certainly help, but personally, if I need to carry security devices which weigh as much as the bike does, I ought not to be locking it there.