There's an argument to be made that warriors who die in battle are less skilled than fighters who survive to a ripe old age. Cohen the Barbarian springs to mind, and probably onto your horse/lady/treasure when you're not looking... on his way to return fire to the gods.

Right, although this idea is somewhat challenged by the story of Sigurðr who is by all accounts the best, bravest, and most famous of all Norse heroes with exploits that include slaying a dragon and receiving personal assistance from Odin on multiple occasions. Sigurðr Is stabbed by his brother-in-law and is able to actually cut the guy in half before dying himself but is then attested as going to Hel in various ways but never to Valhǫll.

It’s unclear why this is and I haven’t seen much discussion about it in scholarly discourse. There is, of course, lots of discussion about what Hel really is/means. But it may have been something implicit in the story that the ancient Norse would have inferred as being obvious. For example, maybe he lost favor with Odin by rescuing the Valkyrie Sigrdrífa from the sleep curse that Odin had placed upon her.

This sort of an idea shows up in Sonatorrek, ostensibly written by Egill Skalagrimsson. In that poem, Egill is lamenting the loss of his son who drowned in a boating accident. In that context, Egill talks about this tragedy in terms of Odin having broken off friendship with him. As a result, Egill has decided to cease sacrificing to Odin, and the consequence is that he now has a vision of Hel standing on the headland waiting for him.