I do have a Pelican case with regularly changed silica gel .......but I fell into the habit of often leaving the camera out 'ready to use'. When I left it in the case inevitably birds had gone by the time I'd pulled it out of the case & assembled the lenses.
The Sigma lens is still good. As are all the lenses.
Camera I have just bought is a full frame Sony A7III. The ASP-C (crop frame sensor) lenses fit it & I'll use them for the time being, but they only use a portion of the full frame sensor, & the effective focal length is shorter, which much of the time wont matter, but the output is only 10 Mp instead of the camera's full capability, so in a pic like above heavy cropping would see the image degraded more. It also means that whilst using crop sensor lenses I can't make use of the full frame's superior low light capability. Problem was , because of the worldwide chip shortage, Sony decided to concentrate on their full frame range & I wasn't able to source another A6500/6600 & needed a camera here which could use the lenses I have. Could have got an A6400, but for some reason it doesn't have inbuilt image stabilisation which I now consider essential. (Better still when combined with a lens that also has inbuilt image stabilisation).
I would have liked the newer A7IV as it has bird eye tracking autofocus, but couldn't justify an extra $1k just for that. As it is my wallet is still in recovery mode from the A7III body purchase! I've seen pics of birds in thick bush taken using the bird eye tracking & they have been pin sharp. Only way I can achieve that is using manual focus, & this relies on the bird staying still for long enough for me to adjust the focus, which, especially with the big Sigma can take a while.
The Sigma is the only full frame lens I have, & to be honest whilst it does the job, I am finding it to be a bit too heavy & bulky. Pointing it at a bird, all too often the shot I want is just after I've lowered the camera because my arms are aching! MrsTea has told me I can buy the Sony Gmaster 100-400 zoom lens with a x1.4 Sony teleconverter. This will give me 540mm so not too far off the Sigma, & quite a bit lighter (Also a lot more expensive! ), but I think it'll have to wait until we are back in Vic next year. For now I have to get used to the Sigma only giving me 600mm. (On a crop frame camera it gave me 900mm).
How are you finding your Sigma?