We are a commune of inquiring, skeptical, politically centrist, capitalist, anglophile, traditionalist New England Yankee humans, humanoids, and animals with many interests beyond and above politics. Each of us has had a high-school education (or GED), but all had ADD so didn't pay attention very well, especially the dogs. Each one of us does "try my best to be just like I am," and none of us enjoys working for others, including for Maggie, from whom we receive neither a nickel nor a dime. Freedom from nags, cranks, government, do-gooders, control-freaks and idiots is all that we ask for.
5X5 is one standard, but it depends on your goals same as everything else in life. Just one set of 5X5/wk is better than nothing but will not be enough to become a powerful lifter.
Because my goal is to maximize general fitness, endurance, and energy, and to minimize deterioration rather than to become a serious powerlifter, I alternate every couple of weeks between 5X5 heavy, and 8-rep pyramids of, say, 6X8. I also throw in one set of rack lifts/wk to work on my sticking point with my max lifts. Why not? It's just more mental and physical challenge. It builds character and sex appeal.
Remember that when we discuss weight training we mean to integrate it into the Maggie's Fitness for Life program which means approximately 2 days calisthenics, 2 days weight training, and 2 days of cardio with lots of HIIT. Around 6-7 hrs/wk, not including sports and recreation. Also, appropriate nutrition for fitness of course.
No promise you'll live longer, but guarantee you'll live better and look better.
The deadlift seriously taxes the nervous systems and high repetitions are difficult to recover from for older athletes. I preferring working up to a heavy set of 3 with no more than 10 reps total for work sets. Slow steady progress.