For portrait retouching, I usually do basic calibration, color correction et c. in Lightroom. Then I proceed to Photoshop (right-click → edit in Photoshop) to do skin retouching and styling. Then I save the image (as TIFF with layers by default), at which point it gets automatically imported into Lightroom, where I do the final stylisation. However, if I go back to Photoshop to retouch the image any further at this point, once I overwrite the TIFF with Photoshop, Lightroom resets all the development settings for the TIFF (not for the original RAW file though). I can get my settings back by selecting the last entry in the development history or using snapshots I created earlier, but it's still a bit annoying. Why does Lightroom reset the development settings when I save over the image in Photoshop, and how can I circumvent it (I think it doesn't happen when I use PSDs instead of TIFFs, but that's only a workaround)
I think it's a LR bug (feature) in a recent LR or PS release. I work like this too (and with TIF files) - it's only recently I've noticed this behaviour (I've been using LR since v1 (and PS CS3) and while it has occasionally happened before it appears to occur more often, but not always, with the latest CC LR/PS).
Invalidating the develop settings would appear to be correct if the image dimensions have been modified (and I've definitely seen this behaviour), but otherwise it has worked as you expect for ... forever (until recently).
When you select Edit in->Photoshop is there a dialog asking you what version to edit? I get a dialog asking whether to edit the original, a copy, or a copy with adjustments.
This Adobe help page has info:
If you want your new Lightroom adjustments preserved, try selecting that option.