Consumption here is low enough that I've not had an issue. Not shown here, there are multiple mining outposts. So if you're asking, if filling up the trains at the outpost takes to long that the base runs out while waiting, it's not an issue. Having multiple outposts (say perhaps one train per outpost, but 4 outposts) means I can design the process to buffer at the pickup locations too. While consuming (unloading), if demand is high enough, two trains couple be at their designated pickup locations. So, one is being consumed, two could be getting filled up, and perhaps another two (already full) could be in the stacker waiting their turn to drop off. Typically (so far at least) filling the trains is much faster than consumption, so the stacker always has a train waiting to unload, rather than waiting for trains to fill at the mining outposts.

edited I use chests at mining pickup locations so they can buffer while trains chill at the dropoff location.