Your bike looks great! Those tires are fine. You could spend more, or less, go fatter or skinnier, whatever you want. I think for your use I would keep what you have on there.
Bearings and chains are cheap and may make a difference if yours are worn. You should check your chain with a chain checker or by just measuring it. If your sprockets and cogs still look good you can keep them that way by making sure your chain is in good condition. A rusty chain should be changed. But, a new chain may skip or run rough on worn sprockets. If that happens you can run the old chain until you replace whatever cogs or sprockets that are worn.
Often you may not notice much difference in any one thing you do maintenance-wise, or replacing a worn part, but it all adds up. Making sure your hubs, bottom bracket, chain, & headset are all spinning smoothly, and your wheels are true, and don't forget the jockey wheels on your rear derailleur, will make your bike ride like new.
I think 70 miles on a mountain bike is impressive!