Pg 288
'The spell is cast like evocation:
power first, control later, all done in
one exchange.'
Pg 255, 'Gathering Power'
'You can channel a number of shifts in power
equal to your Conviction with a minimum of
impact—just one point of mental stress.'
Edit:
Casting Thaumaturgy at evocation means will obviously include stress, as mental stress is the main means and tool of casting evocations. The timescale though is the question you can summon someone small with Seliee Magic say this takes 7 shifts of power with the duration of a turn there does not seem much you could do with a small fairy in one turn.
Summoning is not a durationed effect unless you specifically choose for it to be so (by, for instance, providing the 'body' for the summoned being to inhabit, in such a way that it that body will limit their time in the mortal world). Otherwise, once they've been summoned they're there until they leave, or are banished (possibly by sunrise).