Man, don't get me started.
- Shields. Yeah, you also probably aren't walking around with those on your back. If you're just walking around in the late medieval or renaissance period, you're probably not wearing any armor - maybe your padded gambeson, but even that's pretty heavy and not something you'd want to be hanging out in in the middle of the summer - and maybe a buckler on your belt. If you thought somebody might jump you in the middle of the street you hired bodyguards to stand around you.
Damn, you got me started.
First, if you're in the late medieval or renaissance period, you're probably not using a shield at all. Plate armour and firearms make shields pretty much redundant. During earlier periods it was indeed common to carry your shield on your back - many shields had a leather strap called a "guige" which was for exactly this purpose.
BUT - don't even think of trying to fight with a shield on your back. For a start, it gets in the way and you bang your elbows on it. A lot. Believe me, I've tried it and I got really sore elbows. Second, it's fairly weighty and it swings about getting in your way and throwing off your balance. Third, if your shield is on your back, it's pretty much useless to you as a shield. You can't use it to block blows, and that's what a shield is for. Fourth, don't get ambushed. Just don't. Because it's a real pain in the ass to get a shield off your back and into a useable position on your arm. Seriously - it takes ages. Ages to get it off your back, because if the strap is tight enough that the damn thing doesn't hang around the level of the backs of your knees then it's awkward and difficult to remove it from your back. And ages to bring it into position on your arm, unless it was a Viking-style punchgrip which was transported on the longship and not on your back anyway.
Transporting your shield by hanging it on your back from its guige is perfectly reasonable. Carry it, march to your battle, then stop and get it into position well before doing any actual fighting. Bucklers were known from the C12th and lasted for quite a while, but even those bang around a lot against your leg when you walk (the origin of the word "swashbuckler").
And oh god here I go. Someone please stop me.
Wearing armour all day. It depends on what period you're talking about, and what region. What most people think of as "full plate armour" was fairly late - around C15th, and yeah, it took ages to get into it. Most northern European countries are pretty cold though, so unless you're going on a crusade to the Holy Land you're not going to have a problem with heat. Oddly enough, it was during the crusades that the surcoat and mantle were invented. The most famous Italian armour was Milanese, and that's pretty high up towards the Alps. It can get pretty hot in summer yeah, but for most of the year the weather is mild to cold. You don't usually hear about Roman, Napoli or Palerman plate armour. Most of the other well-known styles of armour (Gothic, Maximillian) are from Germany.
During a tournament, you'd gear up before your first fight, then you'd just stay in your armour. It takes so long that it's just not worth it to get in and out of it all the time. But you also wouldn't be going on long marches. You'd be staying in your pavilion, sitting down and drinking watered wine.
Before the plate period, it was quite reasonable for people to wear mail armour all day. I've done it. Mail is heavy, but you get used to it. It feels really
nice when you take it off, but it's often easier just to leave it on. The best way to transport mail is on your body. You don't want to be carrying it. Put it in a box on a cart, or wear it. The more you wear it, the easier it gets to wear.