Ok, here's some math for you.
So you say you'd start your first part of the trip climbing 1200ft for 18 miles through small town traffic of speeds between 35 and 45mph. Then you hit a downhill slope that's a 2,200ft drop for the next 16miles on a 55mph highway.
The in town energy use can vary a lot depending on how many stops. For me, I seem to average about 3.5mi/kWh through town, no heat or A/C, on flat ground. At that rate, plus the 1,200ft rise, you'd use 7.14kWh (about 36% of your battery) for the first 18 miles. If you don't have many stops you might be able to use as little as only 6kWh (about 30% of your battery). On a rough day pushing through snow you'd use around 9.2kWh (or about 46% of your battery) to get to the top.
Next, you'd go down 2,200ft for 16 miles at 55mph. That's plenty steep enough to have to use regen braking. If you do 55mph or less and the grade is pretty consistent you might come out even at the bottom. Or you might use about 1.72kWh (9%). Of course snow and AC or heater use could change that. Say you're going through some snow and such, you could use 2.7kWh (14%) or more.
So you get to work, best case scenario likely being about 7.72kWh or 39% battery use, and worse case scenario being about 11.9kWh, or 60% battery use. You'd have 10 hours to charge up another 50%, so you'd have either a full battery or pretty close by the time it's time to go home.
Now on the way back things will be different. You'd have to first climb 2,200ft for 16 miles. That would suck up at least around 7.22kWh (36%). Or in worse weather, perhaps 8.24kWh (42%) or more. So you obviously need to charge at work to make it.
Next would be the small town traffic. With your small town traffic you'd likely use around 3.14kWh (16%) with no heat or AC. Or around 6.2kWh (29%) through bad weather.
So you'd need anywhere from 10.3kWh or 53% to 14.4kWh or 71% to make it back home.
No heat, no AC, no snow, driving sensibly, you're looking at getting to work with 61% battery capacity still left (41% if you charged to only 80%) and then getting home with 8% if you didn't charge at work (100% from home), or you could charge up to 100% or 80% at work and get home with 47% or 27% respectively.
So a worse case scenario would be (assuming you charged to 100% knowing it's going to be winter) you'd use 60% to get there, only able to charge to 90% at work, and then get back home with 19% still left.
If you could get a 240V EVSE at your place of work you could always charge to 100% and allways have enough to make it home with 29% or more left on the battery. Or if there were a 240V somewhere on the edge of the small town, about half way between you and your job, you'd be set for just about the worse of the worse case scenarios, even after you lose three battery bars. You could also wait another couple hours at work waiting for the snow to settle down in such a worse case scenario and at the same time finish up charging to 100%.
Conclusion of the conclusion
If you can charge at work, even off of 120V, you should be able to get to your work or home with at least a 29% charge left in a worse case blizzard scenario. And I'm calculating off of my experience with subzero, Coloradan, blizzard weather, so you'd probably never even reach the 29% I calculated, and always make it home with plenty more. That would mean even after the battery degrades down to 9 bars, you'd still have enough range left to make the trip.
2013 SL, 40,000 miles, 12 bars.