You'll see several previous threads here discussing container dahlias that may help you. About half of my dahlias are in containers and while they rarely perform as well as soil dahlias, they do well enough anyway.

The absolutes are they must be in well draining soil if by all year you mean you leave them in the pot during winter. I recently found one of my well draining pots CLOGGED and the soil was literally soaking in water, which destroyed some of the tubers on that dahlia and of course it never bloomed.

If you mean START them and then transfer them, many on here say they do that all the time. My last experiment in moving a dahlia was one died completely after the move, the other sat stunned for a couple weeks but now looks like it is OK, though I have no idea if it will bloom. So I am not a fan of moving them IN SEASON or after sprouting but maybe I just am not careful enough.

Davidinsf, how big are your dahlia containers? Do you fertilize them more often than the ones you planted in the ground?

(Sorry - Just noticed this question)

My containers vary from 8-10" for small and dwarf varieties, 10-12 for the 3 1/2 - 4 ft dahlias and 14 inches for larger dahlias.

They all get fed and watered the same, whether in pots or in the ground. (I know they should supposedly be watered more because pots dry out faster but my soil is sand based and VERY porous and they drain exceptionally fast - so everyone usually gets water as needed).

The trick is trying to decide on water when the fog sets in and they get wet every night. I may actually water the potted ones LESS in those circumstances, since they retain the water better.

David