Here is my checklist
Yearly- Spring prior to first trip.
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Check/Repack Bearings manually, check seals, check brake drums and pads
Check/add Grease to power jack head
Every 6 Months- Spring prior to first trip, fall after last trip.
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Clean roof and awning with spic and span, rinse well
Wash Trailer, dry and wax
Check roof for cracking dicor, leaks, anyplace that needs repair.
Monthly
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Walk around trailer, checking sealant around windows, trim pieces and looking for any other undiscovered damage that needs repair. Fix as needed.
Check battery water levels, top off as needed.
Before each trip
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Check tires for cracking, bulging, damage. Check air pressure.
Check Lug Nuts for rust, tightness.
Check brake lights, turn signals, marker lights once hooked to truck.
Scan and check bottom of trailer for any issues underneath (Hanging coroplast, loose drain cover, loose wires, etc.
Check W/D brackets for tightness
Spray stab jacks with silicone lub before leaving.
Dab of grease on hitch ball if needed.
Plenty of other camping checklist things but this is my list for the minimum before I pull out.