For a Belgian, personally, I would allow it to rise to room temps. I pitch around 65, then allow it to rise to the ambient temperature of around 76-78, some allow the temps to get even higher. It is a classic belgian technique to get more of the fruity/funky goodness.
Also, normally for a 3.5 Liter starter it would require 2 vials or smack-paks to reach the 304 billion cells that are required for your 1.085 gravity, however, that is for near full attenuation in an 18-24 hour time period.
Since you did not step up your starter, and pitched only single vial, it would definitely take a bit longer to see any activity (if there would be any at all).
As an example I made a starter with a vial of WLP 540 Belgian Abbey IV Platinum strain, no krauesen or visible activity, but it smelled nice and funky, and this was before I had a stirplate, when I swirled it I could hear the fizz of co2 coming out of solution.
So RDWHAHB, just give it about 36-48 hours because of the larger size of your starter, and it should be gravy. You could definitely let it go a bit longer if you have the time, however, I like to pitch at high krauesen when the yeasties are ready to rock!
Let us know how it turns out. Brew on