Agh! I miss my spiders!! (I had about 25 not too long ago, but being forced to move means..well...let's just say I'm struggling to find a landlord who's cool with a parrot, bearded dragon, four ratties and a ball python.)
Growth is not a linear process and depends on food availability, temperature, sex and species to name a few things.
Males mature faster (and die younger) than females.
Warmer temperatures and more food (although excesses of these promote shorter lifespans) will usually result in faster growth.
Species have individual growth tendencies. Some grow much faster than others.
All in all, could be a couple years, only a few years, or many years.
All tarantulas (captive-bred or not) are 'wild' in that they are not really neurologically designed for interaction or affection. They are very primal creatures really---they respond to threats/potential threats, potential mates, light/dark and possible prey. At best you are simply another 'thing' to walk around on and at worst you are a threat and need to be scared off. They are really a 'hands-off' pet much like a fish and prefer not to be disturbed.
As per getting bored or entertaining them....nope. Again, they pretty much sit around waiting for any of the aforementioned stimulus and otherwise sit still in their webs or burrows or do some repair work on their homes. Sometimes they'll take a walk around the enclosure to see if anything is new. Ambush predators with low energy requirements and low energy expenditure habits at their finest.