I have an Onix OA21s still that I use in my garage work shop. I go by Dowser's idea, only leaving it on if I plan to return within a day.
This is another of those debated topics on other forums regarding all gear. It saves warm up time but I am not one who leaves everything on. First, I have 5 full hifi set up (Sonneteer Orton, Rega Brio R, an HK and a Marantz.) That would be a lot and I have the light police in he house to make sure we don't waste power. In spite of her best efforts we have only cut the bill from $100 to $80 per month, which does not include cooking, heat or hot water except the circulating pumps. I don't think the cost is such a big deal but it seems that leaving it on all the time could shorten it's life. Some who know more than me disagree.