More damage is being done by not/short driving your SL....than by driving it:
-Gasoline breaks down in as little as 30 days; I doubt most use 16+ gallons every month
-Not bringing oil up to >175 Deg F to burn off condensation, unburned gas (see below), etc
-Unburned Gasoline / contaminated gasoline leaking down cylinder walls from just start/stop (moving car in garage / drive)
-Oil film drying off cylinder walls; rings scoring walls
-Brake Fluid absorbing moisture that isnt minimized from use of brakes
-FI pump seizing or injectors gumming up from old gas (see above)
-Seals / gaskets all over engine drying from lack of use (fluids not engorging gaskets/ heat cycles of metal fitment)
-Expensive Michelin tires flat spotting / dry rotting
-Exhaust system not reaching hi temp to burn off condensation
-Electrical contacts developing corrosion or bad connections
-Fluids separating, condensate, congealing or leaking
-Draining battery with starts and short low RPM drives with alternator not charging battery.
-Microscopic Mold / Mildew / Dust settling on all natural surfaces that would be destroyed with ventilation, heat, UV rays.
-Vermin in stationary car
-Dirty car cover trapping dust; scratching paint, chome, glass; canvas not breathing.
-Paint / Chrome / Canvas / Leather / Wood not benefiting from normal cycles of use, ventilation, wear, wash and polish.
-Storage damage w.HVAC: rubber, leather, wood window seals contract, shrink, swell, dry out w/ moisture / heat / dryness fluctuations.
I could go on; the vast majority of issues posted here are not from normal use but lack of use. ALL machines require normal mechanical rotation, fluid movement and heat cycles to lubricate, and surfaces benefit from protective coatings.
This "
but always started on a regular basis with a quick drive around" does alot of damage per above; you are just introducing fluids into your car that would normally be burned off; a 15 min drive wont burn off anything. Hit a highway for 30-45 minutes at 75 if you want to accomplish periodic preventative maintenance.
In exotic car world we say: "not driving your exotic car is like not making love to your wife, so her next husband can enjoy her more"
Granted no collector car owner heads out in thunderstorm; but, I would never lets clouds, forecast, or light mist/fog/drizzle stop an outing.
Drive her hard, with both needles straight up, and flush fluids/filters every 12 mos; thats it.
Re: Theft Loss
I assume you have Agreed Value Policy; if a loss occurs you will get a check and probably can replace with SL in even better condition, given price appreciation. So not sure why not use it, your not staying in a camper because your house is seven figures...