The only thing I can offer is my personal experience which may have some relevance. I'm 55 and just started lifting again at the end of last summer after what was or the most part a 15 year hiatus. When I lifted I worked out regularly and with no coaching I got up to 2.3 times bodyweight deadlift with no belt. So I was no freakin strongman but I felt pretty good for a desk jockey. And I had plenty of mass for my age. Then I started my own business and completely fell off the wagon. I probably lifted about 30 times total over the last decade and a half.
When I did try to get going again I would find that I maxed out a work set just about what had been my warmup weight back in the day. Then my back started hurting and I got a diagnosis of Degenerative Disc Disease about 10 years ago, so any thoughts I had about lifting again were dashed because I loved deadlifting and squatting heavy more than anything, the two things I was told not to do.
So for a variety of reasons I finally broke the streak and started working out 7 months ago. What I found was that after 6 weeks of working out in my basement, principally dumbbells and bodyweight, I felt and looked like a different person. I can't say that I packed on a lot of mass, but if you used to work out, don't worry about the age thing. A little bit of work goes a long way. Then when I saw the progress, it made everything since then easy. I realized the reason I never lifted during that long layoff was that once I lost my strength and mass after 40, I believed deep down that I could never get it back. I realize now how demoralizing and wrong that was.
Right now, I'm taking a very different approach to lifting. The golden rule is keep safe, avoid injuries, and keep going. I find that focusing on form, limiting ROM, stopping my sets at least one rep shy of failure, all the stuff that back when I was younger I thought was wimpy, I follow religiously and still see great results. So for example, to save my shoulders I don't bench anymore, I do dumbbell floor presses with a neutral grip, all very shoulder friendly. I'm up to 5x5 with 70 lbs in each hand. I feel and look stronger. And I can't wait to work out.
I thought my biggest issue would be working my legs while avoiding the heavy weights, and I was right. But there are some really great articles on this sight about unilateral leg exercises and how to work your quads while protecting your knees. There's plenty to work with. I'm no Tom Platz, but I'm not self-conscious about heading to the beach.
In terms of adding volume, there are tons of articles on this site and around that can help. Lately, I'm working off of some stuff I read from Pavel Tsatsouline suggesting working a weight that you could do 7-8 reps and keep the sets at 5 reps, then do lots of those sets. I do 5-6, he says you can go up to 20. Point being that you get plenty of benefit without working to failure. It's easier on our aging bods. (See Chris Shugart's interviews with Tsatsouline, The Evil Russian Speaks, parts 1 and2).
And now I'm just getting into kettlebells. These seem like a great way to keep intensity high without subjecting our backs and knees to stacks of plates.
Bottom line, great satisfaction awaits if you can get yourself back into it. I feel better at 55 than I did at 45.