The holes in the sides of a container that's going to be sunk inground make it much easier to lift in the fall. I leave the plants that I've lifted in the same container while they are wintering over inside but I do uncover the bottom drainage holes. I seal them back up before they go back in the yard. I don't refresh the soil in the containers that are going to be sunk in the yard but I do ammend the soil where the container will be planted. For plants that I keep in containers I don't go crazy trying to remove all the old soil. I just shake off what is lose, trim any nasty looking roots and repot in new soil. I use Fafard 3B potting mix for most of my container plants. I do save the entire plant when I'm wintering them over but I also take cuttings from them. For the brugs that will remain in the ground over the winter I cut back the above ground growth and root that. This is the first year that I've left brugs inground over the winter so I'll see if they've survived. If they haven't it's no big deal because I'd taken plenty of cuttings in the fall.
Karyn

xerophyte,
I think one of the main reasons why people do bucket of brugs with cuttings is due to saving space. It is easier to put several/to several 100 cuttings in one bucket without rootballs to store and overwinter that way and get them going for spring to plant themselves or have rooted cuttings to trade.
The planted pots with holes in the sides, like karyn said, are easier to dig up in the fall while still letting the plant get some nutrients from the soil and keeping the roots cooler while it is "planted out" for the spring/summer/fall.
Another way I've seen in photos that some people and professional gardens do is : wrap wire like strong rat wire or hardware cloth aroung the rootball when planting it out. The roots will grow out through the holes and supposedly it is easily lifted in fall and placed in a container for the winter. I dont know how easily lol - it seems like it would be rooted pretty well in the ground but I don't know for sure because I haven't tried it myself.
Some sources recommend changing the soil every year or two for potted brugs, and mixing part potting soil, and compost with part good garden soil (sandy loam) for mature brugs. Also I have read that they do well with bark added into their soil. I do add bark to mine. Last year I also added cedar shavings to all my pots and they did great. This year I will add some pine needles as well. Fo me, seedlings and small cuttings do well being in straight reg. potting soil with a little perlite mixed in, because you are going to be 'potting them up' to larger pots as they grow.
It seems that everyone has different ways of growing brugs based on thier climates, water pH etc. and what works for them. For example: When I lived in a more humid climate that got alot of rain I used a much looser potting mixture than I do now that I live in a more arid climate.
It sounds like your brugs are doing pretty good - so you must be doing something right :)
~SJN