The filters can become tiresome, for sure - I personally think the gasmask filters are bugged. Except for a few specific filters laying around, you can't pick any else up unless you only have a few left. The only way I was able to manage the Ranger Hardcore mode was to purchase as many filters as possible in Riga and Market - even still, I came close to running out entirelly towards the end of the game. Combined with the above "bug," Ranger modes only give you another minute or so per filter found - it's less than what you'd get with easier difficulty modes. Otherwise it's an outstanding game - I just wish it was a little more open for exploration and such . . . maybe 4A will release a 2nd DLC with a different quest or something. I've already played through the storyline 4 times to complete the achievements . . .