^ Well since IV administration means a faster onset/absorption, wouldn't that also mean that the drug will be eliminated faster compared to other ROAs? The half-life can still be the same even though the body may eliminate the drugs at the same rate. IV bupe reaches peak plasma concentration is only 0.41 hours (according to the wiki page) which is a lot faster than with other ROAs, so its going to begin to be eliminated quicker since other ROAs will still be increasing in concentration while the bupe in an IV user will already have peaked and started breaking down.
Here is my analogy, which is in The Parable of the Good SuboxMan:
Two men are building fires with logs to keep warm. IV man puts all of his logs into a single pile, and lights them up all at once. Sublingual man starts off with a few logs, and has decided to add several logs every half hour throughout the night. IV man has a big fire rather quickly, keeping him very warm, but after an hour it has already peaked and is starting to burn out. Sublingual mans fire isn't as large, but is definitely keeping him adequately warm, and as each set of logs begins to burn out, he is still adding more to off-set them.
Sublingual mans fire burns throughout the night and into the morning, keeping him nice and warm. IV mans fire burnt out in the middle of the night, which made him get the chills, and have trouble sleeping (symbolic of ye withdrawals). IV man, in a cold sweat, turns to sublingual man to ask him his secret for being able to make his fire last longer and keep him warmer longer than him. Sublingual man replies "that which is not present, can not yet be destroyed" which in layman's terms meant that the logs that were yet to be added to the fire could not begin to burn up yet.
Sublingual man is more like transdermal patch man looking back at it, but I'm sure you are all wise enough to learn the lesson. Peace be with you.