Why not row 5k to improve 5k?

[Sakly]

Probably "lifting to failure" has a different meaning for Mike.
If I lift to first rep I can't properly lift, this is not failure in terms of absolute strength as I could lift the next rep as well, but with less good technique. When understood correctly this point is his "failure point" and that matches well to the clause "don't lift to failure" if failure means you cannot perform the last rep anymore in this case.

In the end you are on the same side.

[rainman]

... if I was to take the approach of doing say 2 x 2500m intervals at 95% effort, how would you suggest to gauge that 95% effort? Perhaps by reducing my personal best 5k 500m pace by 5% and setting the pace boat to that for the intervals?

Try RPE (perceived effort) rather than any objective measure. Picking a good starting point like "reducing my personal best 5k 500m pace by 5%" is excellent, then adjust that up or down for your next hard session depending on how you feel. 95% by watts is not the same as 95% by split time, etc., so take 95% to mean "working very hard, but not working to failure or exhaustion" rather than 95% of some objective measure.

For short intervals (say 40 seconds on, 20 off), if you stop when you think you can do one interval more you are likely at the right load level. If feel like you can do 5 more, then next time do a couple more intervals or hit a faster split. For short very hard intervals you can try something like Improving split times on each interval during the workout -- if you can't improve the split compared to the previous then its time to stop. You need to know your capabilities to make this work well, but you learn them pretty quickly if you try this. Aside: You can also see what not to do with short intervals. Don't plan to keep doing intervals at pace until failure when your body makes you stop.

For hard continuous pieces and long hard intervals like 2 x 2500m, if you think you could have gone faster or longer but it would have hurt then you are likely good. If on a long hard piece you are dying and you need to handle down, then do it. But adjust the rate/pace/duration so that next time you won't need to handle down again. Training your body to stop in the middle is not good. If you do your hard workout and feel really good then bask in the victory and use a harder pace/duration next time. Having victories every workout is much better than being at the edge of failure. Save that edge for personal best attempts.

For strength training, stop when you have one more rep left, rather than lifting until failure. If you don't do any strength work then consider doing something one day a week. Strength work fills a need that erging does not completely hit.

Thanks for another great answer.