Okay i think the original example may be something some people are getting hung up on lets rephrase it.
1] you can use a block instead of a defensive skill roll, when doing so with evocation the strength is equal to one shift a level and you can use it an extra time per shift put into duration also for some reason called persistence.
2] when useing a block in place of a defensive roll with thumaturgy, it works as above but the base duration is scene, you use the time duration chart instead of +1 round, and the block does not go away after it is breached as per the ward/veil rules.
3] can you use a "block" instead of a non defensive roll [ie alertness for initiative, fists to attack,might to lift or break things]? My current understanding based on some of iago's older posts is yes, but there may not be a lot of RAW to support this.
4] can you use the magic system to gain a +x to a skill roll instead of a "block"? Again some of the moderators earlier posts and a few examples in the book support this however there is clearly no listed system for how you would do so in the book.
5] when using thaumaturgy at evocation speeds and methods which duration system do you use? and can you then use the evocation method to boost its duration.
6] when creating a "buff" spell is it most appropriate to use "blocks", aspects, or the temporary powers rules, or some combination of them all as appropriate?
to the OP, by RAW I think if you want multiple checks, you need to multiple the shifts by the times you want to be able to use it. If you want to make a skill check at +10, 10 times, that's 100 shifts. Very expensive.
Go check the evocation building blocks section again, theres no examples of how to get a + anything [unfortunately] though you can clearly get more then one use of out a block by one exchange per shift, my question is weather they need to be consecutive or not, i personally want to say no, and that you also have to spend successes on the thaumturgy duration chart to extend the spells duration. permitting you to get the effext y times over z duration.
Would the player be happy running into a warlock pulling the same trick? Sauce for the goose and all that...
Yes. and in fact i use similar effects in the games i run. i do not however use "plot level" npcs instead preferring to stat them so its likely just a difference in preferred scale. What im trying to get peoples opinions on is more if its RAW then if its balanced. myself and the relevant gm have already discussed most of these topics extensively and figured out what will and wont be allowed in that game.