Potential for Off-Flavors If Let Dubbel/Tripel Sit in Primary

I've read much of the debate on the merits of moving to a secondary fermenter, the main benefit to doing so being a clearer beer. What I am concerned with is the flavor effects on either a belgian dubbel or tripel. I know both require a good deal of aging. In past, more simple brews, simply letting it sit in the primary for a couple weeks has served me well. For higher gravity brews like these, does the potential for off-flavors develop by letting it sit on the yeast in the primary for an extended amount of time. I am averse to secondary fermentation, but would the flavor be significantly increased by doing that as opposed to letting it sit in the primary for a month or so, then aging it for a long time in the bottle?

Your method has merit. Several people forgo the secondary and keep the beer in primary for up to one month. You could bottle age for extended times with good results. Personally, I would age the entire bulk of the beer in a secondary and then bottle, any particular reason why you are against a secondary?

More chance for infection and introducing oxygen. I don't do secondaries anymore, except when I'm dry hopping or doing something like a sour ale where I'm adding the bugs after the primary is done with a clean yeast. A month is no problem for primary. After that, just bottle/keg and leave it alone to age.