I also am usually fine with just exchanging batteries once every few hours. The only exception being very long single exposures, for example if you want to do star trails in a single shot. In that case the battery often runs out somewhere between 1 and 2 hours, and if it runs out it does not save the shot. Of course this can be remedied by instead using the star trails feature or just setting up an intervalometer.
Its not enough of a problem for me to consider trying to connect it to a battery. If I had an equatorial setup that I could leave unattended for entire nights, I might attempt to connect the camera to the same battery used for the mount.
I did a quick google on this, and found that people have discussed DIY solutions
on these very forums.