quick math related to the legendary item thing I mention before
	Spoiler: disclaimer  I know that the method I used is not 100% accurate, but the things I left out (other materials) and things I idealised (100% luck in terms of colors of pieces and items you get) will somehow balance out each other (although the idealisation thing has probably bigger impact on the result) and that's why I could ignore them while doing this
 Scenario 
	Spoiler is absolutely hypothetical and will probably never happen due to all the luck, implausible things and devotion involved in it
you are completely f2p (you can't spend any $ to speed up your progress) 
you are RNGesus, you'll always get set of 10 item pieces of one color as your season rewards and you'll never get more than 6 duplicates (in totall, that also involves the initial item) of each item 
you are the best player of this game (you have to be able to stay at the top of the leaderboard, even above whales with maxed legendary setup, while you have only epic items) 
you are able to be number 1 of the world leaderboard for how much you want 
we ARE counting in pieces from season rewards, because all these other sources are too RNG-based so it's too hard to take them into account (and it's also imho absolutely pointless) 
we ARE NOT taking any other materials (such as parts or power cells) into account, because that would be too hard and it somehow compensates (I think it rather overcompensates, but that's not what this comment is about) the previous point (no other sources of legendary items) 
  Data I used(items per season etc.)  
	Spoiler 
there are 41 items in the game (21R, 5B, 5G, 6Y, 4T) 
you need 6 item dupes to get one item to t5 
you need 246 (41×6) items in totall to get one full t5 set of certain rarity (that means all items of that quality evolved to t5) 
you will get 20 legendary pieces a month (10 per season, two seasons a month), that means 2 items a month 
you can get 24 items a year from season rewards 
  Results 
red: 5.25 years 
	Spoiler: that's how I got this result, same for every category  you'llneed 126 items (21×6), if you keep the rate of 24 items per year (2 items per month), you will need 126÷24 years, that means 5.25 years
  
blue and green are 1.25 year both (30 items required for both) 
yellow is 1.5 year (36 items required) 
teal is 1 year (24 items required) 
that means you will need 10.25 years to get all items  
 
	Spoiler: what does this mean?  This means that even when you are the best (being #1 for that long time) player in this game and also RNGesus (getting only what you need and nothing more), you will need 10.25 years (!!!!) to max out all legendary items in this game.