Top Rated: Head Torches (Main & Backup) & Flashlights
Category: Head Torches, Headlamps (Budget & Sub Zero Lighting)
If we had to choose just two torches (a main + backup) for year-round use, we'd go with Petzl's Actik Core with the e+Lite emergency headlamp as backup. Both are superb performers, both natively use lithium-based batteries; the rechargeable Actik can be topped up and the e+Lite's CR2032s weigh almost nothing (so plenty of spares won't weigh you down or fill your pack).
Being a "fear the worst, hope for the best" kind of person, I would still like an additional (third) torch for multi-week treks. In this regard, a case can be made for both the iProtec 100 (or a similarly reliable lightweight single AA battery narrow beam torch) and the Petzl Tikkina (especially now they're "Hybrid" and will accept the Core battery from the Actik should it fail). I think the choice comes down to how much night-trekking you expect to do. If you want an additional backup for the Actik to cover its ability to light the way through treacherous terrain, then a torch like the iProtec 100 (with an Energizer Lithium Ultimate AA) would serve that purpose. If you want a more all-round backup and feel the e+Lite is more of a last resort, then an empty Tikkina (at 49g) would fit the bill.
Finally, if you engage in long distance treks but don't venture out much below -5°C, I would suggest that two or all three of the torches mentioned in the "budget options" section would suffice. They've served the Scramble team well, and were certainly good enough for me over the 8 days of this year's (2020) winter kit test.