SO just as the title says, I practice about 2 hrs a day broken up into 20 min segments about how long will a deck of cards last and when do I know it is time to replace them. ALso are cards ready to go out of the box or do they need to be broken in?

I like to practice with the deck in various states of wear, so I make a practice deck last quite a while, even over a month. Some techniques are easier with a new, slippery deck, and harder with a worn deck; other techniques it goes the other way. I like to practice everything both in ideal and not-so-ideal conditions. When I open a new deck I take a nail buffer to the edges, do a few faros and other shuffles, and then get to practicing.

It's all subjective. Depends on what effects you want to perform. I worked restaurants for MANY years.
I always had people sign cards that I would give away leaving me with incomplete decks. I saved these decks and would use them to replace missing cards over the years to make complete decks. So, in order to save money, I never disposed of decks until they became a little too dirty. Not a good look.

Also I would many times use new deck in performance and didn't have to break them in to perform. I might have casually shuffled but that was about it for the effects I performed. Never throw out cards, you can always use them to practice a MCF ( Mercury Card Fold) you will want to learn and other neat things. Like making a frog or T&R card.

Same here. I heard about Harry Lorayne using old worn scotch taped together cards and that sounded like it should always be an option. But new cards are fun too. But broken in cards faro easier. Versatility is great.

I also like to be ready to perform with someone else's deck. It doesn't happen often, of course, but when the opportunity arises, it really does make a difference. Last time I did it, they had a souvenir deck from somewhere: looked nice, brand new, but not a good deck for handling. It wouldn't faro or even do anything like a weave shuffle. It was like trying to faro bricks. But I was still able to have some fun with it, and everyone knew it was not a trick deck or prepared in any way.

Here in Australia, the local brand, called Queen's Slipper, are really terrible cards. I carry my own Bicycle cards, but once in a while I practice with the Queen's Slippers, just to be ready to use them if the time comes.

Yea I never planned on throwing any of them away but at the same time I am the type that will keep using them and struggle to learn. I like the idea of being able to work with different stages of decks

As stated before, this is subjective to various factors. Do you use lotions, sweat a lot, what type of card stock, brand of cards, work in a wet environment like a bar, etc...

A deck can last for days, weeks, months, or years. It all depends on what you are doing with the deck. under the best condition, a deck could last for many years. I have one deck that I shuffle multiple times at work, however, I the 5 of hearts or diamonds have a slight tear in it causing it to catch every time I do a particular riffle shuffle, otherwise, the deck is still in working conditions.

I will say that despite my fascination with versatility those crappy dollar store decks have torn up my hands before.
But I've never thrown away a deck unless I'd torn it in half (I used to do some strongman stunts too.)

I'd recommend:
A) Washing your hands every time
B) Rotating two decks for practice (it gives them some time to "breathe" and "reset", Idk if it's just placebo or not but I've found it extends the average lifespan by way more than 2x)
C) Maybe investing in a Proper Card Clip

Honestly it's impossible to say how long they last because it depends what moves you're practicing and what you're trying to do. Never throw decks out of course, there's always something you can practice (TnR or Mercury Folds for example)

On the topic of keeping cards new, is buying the sleeves to keep decks in worth it? Some are metal but I've seen some plastic ones as well.