I can't remember how many years ago it was when DC did a double miles deal with DL. I didn't fly DL much but this seemed too good to be true, and a moved a lot of points. Since then I got the DL AMEX card and have used up a lot of DL miles obtained through DC and AMEX.

So here's my dilemma. I do fly UA and accumulate UA miles in various ways, often giving them to relatives to come visit. At the moment I have plenty of UA miles for what I can envision for the next year or so. My question then is whether to convert DC miles to UA to get the 30% bonus at a time when I don't really need them. I know if it were double miles, I would do it in a flash.

What experience do people have banking miles with these 25-30% bonuses? Do you feel it's worth it?