In ESX 5 you have to mark all such LUNs as perennially reserved and your ESX boot can be fast as usual.
Here is CLI command to mark LUN
esxcli storage core device setconfig -d naa.id --perennially-reserved=true
This has to be changed on all ESX hosts with visibility to the LUN.
More info at http://kb.vmware.com/kb/1016106