I think it depends on how our feelings affect us. Some people are apathetic and try to go on a holiday..
I don't think I've felt a prolonged lift in my mood, but it's definitely given me euphoria and new outlooks on life, which feel profoundly amazing whilst experiencing them.
It has helped me and I know it's taken away depression at very low seconds [left overs from trips]. I can't talk about any permanent change in mood, although in the last 6 months I've had substantial changes in my mood, although I can't tell you how I used to feel 6 months ago nor my average mood/how I feel often/what a majority of my feelings even are, although there's definitely pain/misery causing suffering to my psyche, but that's another story.
I don't know how you haven't built up a massive tolerance within 3 years of weekly use, nor how it still effects you in such a magical way after so many high thirds. Not that anyone here advocates doing anything illegal

I know that smoking cannabis should always be done when taking DXM.
DXM does have antidepressant qualities, I don't know whether the short half-life affects the length of the nonselective reuptake qualities or how effective they are pharmacology speaking but if they're working for you why change? I've heard of MXE having very good anti-depressive properties and I've thought about trying some, although it seems unlikely right now.
Depression can trigger the onset of insomnia, as with hypersomnia. When I got hypersomnia sporadically although lingering, I was thankful for it because I could just lay in bed for a couple of days. The sleep helped lift my mood, and the primary act of laying down and sleeping altered my sense of time improving things further, and taking the edge of my feelings. Enough about me though, as for the other symptoms depression can trigger the onset of them, but it's possible to be depressed with a fairly normal sleep pattern, enough concentration to exist comfortably (you can also meditate, concentration is built up), they can still be hungry, and enjoy certain activities, as well as not being suicidal, all the while being very depressed.
You can also have periods of time with symptoms that pass.
What do you mean by function
normally? There are plenty of people who have depression and do things with their time, who lead "good" lives, who still exist, people that can get food in their stomach while being apathetic about their existence.
To me it's about being able to function. Having to do things differently, external events impacting you differently, have opposing feelings and views about things, doesn't stop you from functioning, although I do think in many cases it inhibits "normality" and makes it harder to just do what everyone else does because you feel so much worse than everyone else. You have no desire to do something that they have a desire to do, you can still function in a brilliant way, just some of us don't value our time enough to do so, or want a way to escape their reality kill themselves. I don't think suicide is always an act stemming from depression though.
Define depression in whatever way you like, but I personally think it's over diagnosed and dislike people referring to a bit of pain and a few joyless days as depression. Depression is a long term commitment, and I fucking hate it.
I know this was off-topic, continue with your DXM thread