The new UCE-engined Royal Enfields are the most refined models, to date.
However, the earlier models have alot of appeal in various forms, and offer a lot of enjoyment for the money.
Much of what you read about the troubles looks out of proportion a bit, because peole tend to bring their problems to the internet, seeking solutions. Thus, you read about alot of problems. And there are some problems which vary in severity. But many people have long ownership with very little problem or just minor ones.
A good guideline is that the bikes are generally less prone to heavy maintenance and breakage, as they get newer in model year. Improvements have been made each year, and problems overcome, to a certain extent.
Some people actually enjoy the maintenance and modification aspects, so this is not viewed as a "problem" by them, but might be a problem to those less mechanically-inclined.
So, if lowest maintenance and best overall reliability, and higher cruising speeds are a big priority for you, then the newest of the models with the UCE engine will be the first to look at.
If you are mechanically inclined, and like to tinker, and enjoy older technolgy, then either of the previous models would suit you, for cruising speeds under 55-60mph.
I own a 2000 model Bullet with the very oldest engine design, and I enjoy it very much.
It all comes down to what's right for you, and there are a variety of choices that suit various needs.
All of the models will suit a 45mph cruising speed, without difficulty.
One issue that is fairly common on the earlier models is electric starter failure. There have been some efforts to overcome that, and the newest models in the UCE range seem to have totally overcome that issue with a new design. The older models have kickstarters too, so that can be used instead if you wish.
The rest of the common problems are generally avoided with a careful break-in procedure which conforms to the owner's manual. And you need to check nuts and bolts periodically for any loosening. And adjust the chain, and change oil, and stuff like that.
I've never been stranded on the road by my Bullet.