Personally, for what a power supply like a Elk 624 costs and a battery for the cell itself, IMHO, it's a no-brainer to have headroom. I just looked it up and it's 500 mA load, but I wouldn't be surprised if there was an inrush, which I'd have to ask some engineers about.
We still have spotty 4G coverage where our accounts are mainly located, so the installation of 4500's (or the other uplinks) haven't really made much sense for us in our area. For some customers, we provided a cost analysis of what the 2500 costs vs. the 4500 and what the cost of adding the "uplink replacement" monthly on to the account and it makes more sense to just replace the 2500's once the sunset comes to play in our area. I'm sure once the dates start looming, it might not be the case, but right now is a different story.