~100 days... that's a lot! Having never held a "normal job" I can't speak from experience, but it seems like it would be so hard to have a good career that let you miss this much time.
...Although one thing you're missing is the federal law that says they HAVE to let you go. If they don't - you sue and get a big payout.
They have to let you go be a Reservist. That's not the same as
supporting you. If they straight-up tell you "we're firing/not promoting you because you keep going off on these Navy trips," then yeah, you can take 'em courtside and will most likely win. I believe I read about a firefighter somewhere who wasn't promoted to Lieutenant and was explicitly told it was because he might have to deploy with the Reserves, and successfully sued the city for promotion and back pay.
However, there are some horror stories out there of employers sidestepping the ESGR laws. One example I read was of a high school principal, a LTC in the Guard, went off on a yearlong boondoggle vacation to Iraq. When he returned, the school district made him asst principal of the local 'alternative' school (the kind for kids with social difficulties like stabbing people). Techincally that's legal - they have to give you your job back or one at 'equivalent pay and seniority' - but it was pretty clear they were career-fucking him out of a sense of revenge. He took them to court, but I'm not sure of the outcome.
Of the two 'real jobs' I've had since leaving AD, both were in the defense industry, but were vastly different experiences
vis-a-vis my Reserve time. The first job was with a small (~500 employees), notoriously cheap company who begrudged me every day I went Reservin' that wasn't on a weekend. I had to burn time off or go LWOP (Leave Without Pay), and heard a lot of heavy sighs every time I said I was going. All this even though it directly supported the contract I was working on.
The Iron Works, on the other hand, has been extremely supportive. Immediate bosses like it because my Reserve flight time and quals helps keep me current at no cost to the company. Corporate likes being a "Reserve-friendly" company. I get differential pay (regular pay minus Navy base pay) while I'm gone, they're keeping me on my company health insurance at no cost while I'm mobilized, and job will be waiting for me when I get back. I'm not naiive enough to think it's out of a sense of patriotism - I can see all the ways this doesn't cost Corporate much or works to their benefit - but I'll take it.