Wolfwood2 said:
I find the most boring thing about summoning spells is their incredibly short duration. You get to use the creature for a combat and that's it.
A varient might be to allow upping the duration if you choose a single creature from one of the lower level lists. Maybe allow a summoning duration of 10 min/level if you choose from a creature two lists lower than the spell you're casting, and 1 hour/level if you choose a creature three lists lower than the spell you're casting.
See, I thought that as well. Which is why I borrowed an idea from the Kingdoms of Kalamar books. In one of their books (Player's Guide, I think), they introduced the "Scaleable Spell". In essence, a spell that has the Heighten Spell metamagic feat written into it, so it improves in output based on how high a spell slot you prepare it in/cast it from.
The only problem was, KoK executed the concept poorly in my opinion and made some deucedly overpowered spells.
I took that concept and the Summoner's Circle article and combined them.
So what I got was...
Level 1 Summons allows the Summoner Circle CRs based on what level slot you use for 1 round per level. Great for making a combat summons list.
Level 3 Summons allows SC CRs-1 based on what level slot is used, but for 1 min/level.
This continues up on the odd levels, slowly decreasing the maximum CR of the creatures, but extending the duration. This allows a summoner to have very useful/utility creatures for a long duration (can we say Dao?), but not excessively powerful creatures which would unbalance their combat contribution.
It's worked really well in my run, and made for some seriously amusing interactions with summoned entities.