Upgrades: How often?

Mae govannen!

With my characters I gathered some sword hilts, bow strings and other nice upgrade components for weapons + some runes. I know from reading here that you can only use one (the best) rune in your armor for +stats. But what about weapon upgrades? Can you use 2 or more upgrades on the same weapon, or does the second replace the first, even if it is another type of upgrade (say hilt + something other for the weapon of choice)?

Thanks in advance.

The second upgrade replaces the first. Just remember that there are different upgrade parts that influence prefixes and suffixes Lets use a sword for example. A plain white (no upgrades). You can have 2 upgrades on it at one time, just that one has to come from a hilt, the other from a pommel. So lets say you add a Fiery hilt and a pommel of fortitude (health +25) . You'll have a Fiery sword of fortitude with fire damage and a 25 health bonus to it. Now lets say you decide to add a shocking hilt, it will become a shocking sword of fortitude, changing fire damage to lightning instead. Now, lets say you find another pommel of fortitude (health +20). If you add it to your sword, your health bonus will drop to 20 from the 25 you had previously. The good thing is that when you attempt to upgrade, you're prompted if you would still like to do it.

Thanks for the quick and very helpful answer!