I usually do it when it’s safe to do so, e.g. can see ahead clearly and no imminent bend in the road, no gateways, nothing else in the hard shoulder, etc.
Sometimes the passing vehicles aren’t the most courteous in letting me back in, and I have to bully my way back into the driving lane. Which worries me a bit.
A couple of months ago I had a driver gesticulate wildly and slalom after he’d passed me, then extended his right arm over the top of his car, presumably pointing towards the hard shoulder. He’d been behind me for a few kilometres, having passed a number cars in the overtaking lane but then ran out of road, so to speak, and was stuck behind me. However, in those few kilometres the hard shoulder had either been too narrow, or there were side roads, or gateways. There wasn’t an opportune section to pull in for at least another kilometre or so.