Well if you want to support that much memory it means that at some point in the future your sketch will have to allocate that memory and be fine with it - so you can minimise the risk of that memory not being available at run time without notice by pre-allocating it and not depending on run-time dynamic memory allocation.
There are trades-off as always, don't allocate 10 buffers if you only need one for transient use for example, then just have one large buffer that you use for all the temporary work.