I've never been on subutex, but it does have a longer half-life.
It's half-life is 37 hours. But that's just an average & a whole bunch of factors can influence an individual's elimination rate.
For me at least, I was taking a resting period about 6 months ago from all narc meds, & the hardest by far was when I went off the last med. Stopping the first couple narcs did not produce many symptoms. What really threw me was the last one stayed in my system longer than average, so my withdrawal symptoms kicked in later than expected. On average, at the point at which I went into withdrawal I should have had no more than 20% of the med left in my system, but really it showed over 30%. In my case, hydration was a critical factor. Since I was slightly dehydrated I did not eliminate the narcs as quickly.
Different things help different people, so try to find something that will help you handle the withdrawal symptoms. For me, drinking tons of water, gatorade and chamomile tea to finish flushing the drug from my system and curling up under the covers for a day or so helped because I could focus on the fact that withdrawal doesn't last very long and I just had to make it through the worst of it for a few days and then a still difficult, but more bearable week after.
Hang in there! I know it's super miserable & I really feel for you, but you will make it and you will be healthier in the end. Of course, if you get sick too many times or you're having heart problems or something serious then get to the ER right away, otherwise just hang on and remember things will get better in a few days -- if not sooner. Withdrawal is different for every person & each medication & sometimes different from one time to another even with everything else the same, but one thing that doesn't change is that it won't last forever. Hopefully yours will end sooner rather than later. :)
Thinking good thoughts for you today & wishing you a better tomorrow!