Not long after I bought my first Sigma 120-300mm ƒ/2.8 I invested in the LensCoat Neoprene Cover for the lens.
On the most basic level it prevents cosmetic blemishes on the surface of the lens and helped retain value of the lens. Your lens will still depreciate. Take a look here at KEH's guide and you will see how much depreciation is cosmetic.
|NEW||As packaged by manufacturer complete with manufacturer's USA warranty. Not previously owned or used by a consumer. *You have probably seen the words "NEW" or "LOWER PRICE" listed online or in our catalog where prices usually appear. Due to certain manufacturer's minimum pricing requirements, we are not permitted to publish the price if we sell it less than the manufacturer's Minimum Advertised Price (MAP). While these listings may seem inconvenient, it is our way of letting you know that when you call or click-through on the website, you will be quoted the lowest pricing anywhere for comparable items.|
|DEMO||As packaged by manufacturer complete with manufacturer's USA warranty. Never owned by a consumer but used for demonstration.|
|LN||"Like New" Includes original box and instructions.|
|LN-||"Like New Minus" Extremely slight wear only seen upon very close inspection. Box and accessories usually not included. Glass perfect*.|
|EX+||"Excellent Plus" Exceptionally nice. May have slight wear on finish but visible only under close inspection. Glass very clean*.|
|EX||"Excellent" Shows moderate wear. May have small dents and/or dings and slight finish wear. Glass may have slight marks and/or blemishes that will not affect picture quality*.|
|BGN||"Bargain" Shows more than average wear. May have dents, dings and/or brassing and finish loss. Glass may have marks and/or blemishes that should not affect picture quality*.|
|UG||"Ugly" Very rough looking. Multiple impressions in metal, excessive finish loss and brassing. Glass will have marks, fungus and/or haze which will affect picture quality.|
|AI||"As-Is" Usually to be used for parts only. All equipment sold in As-Is category carries no warranty nor return privileges. The equipment most likely doesn't work and may have missing pieces. Defects will include, but are not limited to the problems listed on the description.|
Here you can see the lens without the lens coating and that is how I hope I can keep it looking for a long time.
LensCoat® Lens Covers are manufactured from 100% closed-cell neoprene, offering protection from bumps, jars and nicks, with a camouflage-pattern fabric cover. LensCoat® Lens Covers also provide a thermal barrier, protecting your hands from cold lenses in lower temperatures. They are easy to install and remove, sliding on like a sleeve, leaving no residue on the lens. And LensCoat® lens covers are waterproof, providing protection in harsh conditions.
If the LensCoat performs as well on this lens as the last one I had on my older 120-300mm then I will recover the cost of the $89.
Here is a video explaining their product that was produced by LensCoat.