By this level collectables are definitely overflowing if you haven't yet come up with a plan for storage outside of your medium collectable bag.
My banking plan includes 3 other free-to-play accounts with 3 characters on each account. Here is my storage plan with only the first 2 accounts currently in use for storage:
Account 1
Character 1
- Level 1-5 unbound gear
- Tier 1 collectables stored in a medium collectable bag purchased by my main character and traded to this banking character
Character 2
- Level 6-10 unbound gear
- Tier 2 collectables stored in a medium collectable bag purchased by my main character and traded to this banking character
Character 3
- Level 21-25 unbound gear
- Tier 5 collectables stored in a medium collectable bag purchased by my main character and traded to this banking character
Account 2
Character 1
- Level 11-15 unbound gear
- Tier 3 collectables stored in a medium collectable bag purchased by my main character and traded to this banking character
Character 2
- Level 16-20 unbound gear
- Tier 4 collectables stored in a medium collectable bag purchased by my main character and traded to this banking character
Character 3
- Level 26-30 unbound gear
- Tier 6 collectables stored in a medium collectable bag purchased by my main character and traded to this banking character
Account 3
Character 1
- Level 31+ unbound gear
- Any extra ingredients stored in a medium or large ingredient bag purchased/earned by my main character and traded to this banking character
Character 2
- Rare filigree plus any non-rare filigree I may use
- TBD
Character 3
- Rare filigree plus any non-rare filigree I may use
- TBD
Bound-to-character large bags can be earned by finding planar shards in the Subterrane wilderness and a few quests (see wiki page here: https://ddowiki.com/page/Item:Planar_Shard)
An unbound large ingredient bag is given for Twelve favor. A small augment bags is given for Keepers of the Feather favor.
Also, if you plan to reincarnate you will need to either spend your platinum or level up a banking character on another account to 13 so you can trade the platinum before reincarnating which resets your plat limit to the level 1 limit of 1250.