Time Machine help

Leave it connected, TM will do hourly incremental backups.

You can do as you want, leave it connected (for hourly/daily/weekly backups) or disconnect it and store it somewhere else.

Time Machine FAQ

Anyway, my backup method for not recreate-able data:

I have one 500 GB HDD for my photographs (digital and analog) libraries and editing documents, one 500 GB HDD with my personal video footage in an editing friendly format.
Both 500 GB HDDs get backed up to one 1 TB HDD via CarbonCopyCloner.
And that 1 TB HDD gets backed up to another 1 TB HDD via CarbonCopyCloner.
Therefore I have three copies of my important data.

Click to expand...

You don't have to leave it on/connected all the time. I imagine that it's not good for the drive nor for energy usage.

What you can do is, after a backup, disconnect the EHD (properly, which is to say by ejecting it and then disconnecting it from your computer) and turn Time Machine off so that you don't get those annoying pop-ups all the time.

Otherwise, you can leave your hard drive in (and only occasionally turning it off) but change the time interval between incremental backups or set a schedule using third-party applications. I use TimeMachineEditor to set the schedule and frequency of backups.