The motor comes apart by loosening these two screws.  Don't pull them all the way out as you want to keep the gearbox together as one assembly.

In the past I've dismantled the gearbox further to add grease in the second stage but its too easy to make a mistake reassembling it (there are lots of small gears, spacers etc) that I no longer do this.  I have not seen any problems since making this change. Its probably best just to leave as per the picture.

Remove one of these screws, add a little loctite and replace the screw.  Repeat with the second screw.

I use loctite 2760, this one small bottle has lasted me a long time.  It works well in this application.

Add a little locite to the two threaded holes as shown, add a little light grease to the gears then reassemble the gearbox onto the motor.

Next make sure the metal tabs that hold the rear bellhousing of the motor to the can are fully bent over.  I use a small hammer and a flat bladed screwdriver to fully flatten them.   I've had the bellhousing come loose before I started doing this step and none since.

The above steps are likely enough to make sure your 1000 RPm motor stays together through most fights but I go a few steps further to ensure they do.  The next step involves using "Goop" or "Shoegoo" adhesive.

First I smear a layer of Goop onto the outside of the gearbox and the front half of the motor.  You can use a little less than shown in the picture, a thin layer is all thats required.

Next slide a length of heatshrink tubing over the gearbox and the front half of the motor and shrink it down so that its a tight fit.  The heatshrink and the adhesive will keep the two part together even if the screw that secure the motor do come loose.

After adding the wires (and the capacitor if wanted), I add a little more Goop around each terminal to support the leads. This takes the strain off the terminals on the motor.  I also add a little into the recesses for the tabs that secure the bellhousing.