There will obviously be some delay when you need to load a 170Mb large texture and send it to the GPU. The length of this delay depends on the hardware you run your game on.
You can try to either reduce the size of your images so that the final texture/atlas gets smaller and/or you could add texture compression to reduce the size of the file ( but it will instead add some time when uncompressing instead). You will have to tweak this yourself to try and find an acceptable solution.