Is there anything to worry about with time machine on my macbook pro laptop?
Time machine keeps a local store of backups if the time machine drive is not available. This is transferred to the backup drive when it is next connected, so you don't even miss an hourly save. You can see these highlighted in a different colour if you enter time machine a few hours after being disconnected from the backup drive. 

Source: http://support.apple.com/kb/HT4878