With red as one of its color identities, it is understandable that it gets five defense counters
The ability to play Shatterskull Smashing as a Red-producing land - possibly untapped and on demand - might win the game
Rites of Flourishing is a group hug card that helps all players equally, but it creates a problem in other strategies because you spend your mana on a card that helps everybody
Doctor's companion (You can have two commanders if the other is the Doctor.) Whenever Amy Pond deals combat damage to a player, choose a suspended card you own and remove that many time counters from it
Short answer: it depends on why you collect (prestige vs play vs long-term resale) and what you collect (rarities, promos, graded grails)
Depending on how much you want to spend to optimize your land base and include tutors to search for these combo pieces, you could likely take this deck as high as level five