Exactly this^ is the most-likely scenario. Remember, whatever outlet you're plugging into is protected by a Breaker which should trip if anything bad happens. Only have high-amperage Breakers in your garage? (guilty, my welder and machine tools like to eat) there are other options. Personally I don't worry about it.
Here's another thought which will likely blow some minds; I don't leave everything on a Trickle Charger 24/7. For my purposes I have four Battery Tenders which monthly get used to top-off the charge on the batteries in my ATV's, My two classic VW's are the on the same schedule if I haven't run them in a while. I make a point to ride my Street-legal bikes monthly (even if it's just to the store) so they rarely see a battery charger, but all have SAE ports and cables on them if I do need to charge them. FYI Battery Tender makes a neat little digital battery gauge which plugs into those same SAE ports and will tell you the state of your charge. With this set-up I rarely have battery chargers running all night (though it doesn't bother me if they do) and I rarely have to replace a battery (it's not uncommon for me to get 5+ years out of a battery) plus I don't have cords and battery chargers all over the place, all the time.