Exporting/Saving files from Lightroom and Photoshop Question

I've been editing my pictures from lightroom and move to photoshop if i need more editing like local adjustments and using onone and nik software. My question is, what could be the best PREFERENCES to export from photoshop or lightroom so I could get the best quality of the file to PRINT to RE-EDIT. I am thinking of saving it twice so I can submit the flattened file to the lab for printing and the unflattened file so i can access my layer adjustments when i want to re-edit.

What I mean by PREFERENCES are format, color space, resolution, bit depth, etc that are usually acceptable to most labs without sacrificing the quality when i want to re-edit.

By the way, I'll be using Mpix, Bayphoto and Adoramapix as my lab.

When I send a photo from LR to PS I send it as a 16 bit tiff so I have the maxim quality and latitude in the adjustments that I need to do. A PSD file would be the equivalent.

From there, you can if you wish save all layers/adjustments to that "project file", or at least as many as you can do in 16 bit. The alternatives is if your disk space is tight -- you can convert to 8 bits, flatten the layers -- those are the main things.

Then, to create a print file -- the "universal" format is a jpeg, and it should work fine with almost all printers. They will tell you about specific requirements or recommendations (as in if they prefer tiff or aRGB). But in general a high quality jpeg will give great results. Most professional companies will take high resolution images and can print them in numerous sizes, even larger than what might be considered "reasonable".

I think it's important to initially work with a printer to familiarize yourself with that to expect. If you plan on large prints, crop a portion to print at say 8x10. Check out the colors, the tones, and the sharpness in case you need need to do more work on these things.

In time, get a good workflow going with one or a few printers and things should go OK.