If you are still planning on going to enough restaurants to use the credits, no reason why you shouldn't get the plan if you want it. It would only become problematic if you don't use the credits (that is, if you start skipping your restaurant reservations to stay in the lounge). If you think you will want only one or two restaurant meals for the full stay outside the lounge offerings, DDP is probably not for you.
Outside of the fact that there are some guests who use DDP solely for the convenience of prepayment and don't care whether or not they lose money on it, I can't imagine why one would purchase DDP without intending to use the credits. You may be thinking that you would like to have a prepaid option of going for meals outside the lounge. If the option is valuable enough to you to prepay for it, then you may want the plan for that reason. If you get the plan because you'd like to save money on meals, you need to plan for meals outside the lounge.