These two classes are the main stock of my local lines alongside the 334s and have been my entire life, so I feel I have something of a vested interest in this.
Seeing this development, I am anything but surprised. They are imho the most comfortable and all-round smoothest-riding EMUs in the fleet with the most comfortable seating - you can debate amongst yourselves the evils of 3+2 seating; I personally have never had a real issue with it on the 318s/320s or the 334s in the over 20 years I've been travelling on them - plus they're still capable of swallowing up the crowds in the peaks even in their ever-increasing dotage.
This news also isn't a surprise when one looks at the broader picture, given the invitations to tender for the contract to build their replacements has only gone out in the last week or two and they won't appear until 2030-31 at the very earliest given the complexity and scale of such a order.
With both classes having undergone several major overhauls/refurbs throughout their careers and have been otherwise better looked after than their cousins down south, I can see them staying the course pretty well. It also helps that unlike the 323s, they have a by and large common spares pool to draw from, especially with every other Mk3-based EMU having been removed wholesale from service barring the handful of Varamis 321s. Granted, that spares pool ain't infinite, but it's a sight more plentiful than the 323s.
Quids in for Eversholt to be able to keep milking fully paid off assets for another 5-7 years too, so all good as far as they're concerned.
Just as long as they don't suffer a catastrophic and sustained drop in availabilty/reliablity in this time period, the current status quo will be maintained until their replacements finally move beyond the realm of being a glint in a Argyle Line commuter's eye.
