Just another picture . I really hope to help it become fuller but if I should leave it be , I will . My whole property smells wonderful when it's in bloom, I really do love it.

oh, it's beautiful! I love lilacs!

If you want to rejuvenate it (cut it back or shape it), you do it right after it finishes blooming. For total rejuvenation, the general advice is to remove 1/3 of the branches each year for a 3 year period by cutting them back to the ground. My Dad has often cut back selective branches of older/taller lilacs by trimming them to a desired height... he never had any problems with them coming back.

Yours doesn't look like it needs total rejuvenation at all. It looks a little like one of mine... I had a beautiful Charles Joly lilac that got completely busted back one winter. It must have been grafted and I must have lost the CJ part because what I ended up with was a common lilac that suckers *terribly*. To make matters worse, it got busted up again the next winter and again two years later by construction equipment. That poor lilac has suffered repeatedly and it keeps sending out more suckers. :p There doesn't seem to be any way for me to control it now, so I just cut out anything that's misshapen and excess suckers whenever I have the time and will. :O)

Lilacs tolerate pruning well. In the pictures it looks like a fine healthy plant. There are several techniques available. What do you want it to do?