They will come back in a cpl of weeks, have a good look round then take a chance if they think your are in bed or out of the house. We got done twice in 8 mth both times they were seen on CCTV and house alarms went off, second time took them over an hr to get in. Best bet is a baby monitor next to your bed and one in side the garage, alarm and make sure they are locked up, also pille stuff up in front of the bikes so they have to move stuff.
My bikes are no longer kept at home Because of this. I pay £20 per mth to keep them at a secure lock up with 24hr security.