There is no 'hard & fast' limit in the software itself, but like the rest of the product, memory and speed does have their impacts. BTW, what is your concern, speed of update or interactive performance while adding additional curves and/or constraints?
John R. Baker, P.E.
Product 'Evangelist'
NX Design
Siemens PLM Software Inc.
Cypress, CA
I am creating a sketch with some curves which define some engraving for a part. I have got to the stage where my computer 'thinks' for a long time before creating a new constraint which would not normally cause a problem. Adding the final constraint also tends to make the sketch overconstrained.
Just a comment, looking at the problem from a different perspective perhaps.
Do you need to constrain everything in the sketch? Depending on what you are engraving you may not benefit greatly from constraining everything if you're unlikely to want to change it for any reason. NX works just fine in most cases without having to have each and every sketch fully constrained.
If it is a repetitive patter of some sort you may want to sketch the first instance of the pattern and then build the model with an array to produce several identical copies.