Many string sets cost $15 - $20 by the time they are delivered to Australia or bought in a shop. 50 x $15 = $750. If you change strings every week when you really don't need to it will cost you $750 a year, getting close to the price of a nicer uke. If you have a lazy $750 lying around or if you are a professional musician, this is not really a problem. But if you are a person who is working to a tight budget, it pays to get maximum value out of your strings. Plastic strings can last for several years on some ukes, and they hold their tune and sound ok. Wound strings wont last several years, more like a month maximum if you play them a lot.
In many cases you can get the sound of the uke to change just by varying your playing technique. If you have an action that is 2mm high, you will be surprised when you do some work and realise that you can get three or four fretting heights, each with a different sound, just by controlling your fretting fingers. There are a few cm from the join to the bridge where you can hit the strings, you can learn several picking or fretting positions, each of which will have a different sound. And you can learn how to use them all in a single three minute tune if you feel like it, you do not have to stick with the same technique all the time. Add in a pick, and you get more possibilities. Fretting and picking technique does not cost any money, picks cost less than $1, you can get a lot of mileage out of your strings without spending more money.
I like to spend money on things that last like ukes and music books, strings are consumables, they can be expensive consumables if you are not careful in how often you change them and how you use them.
Realistically if you change strings every week and you know what you like, you would be better off finding a way to bulk buy strings. You either get the fishing line in the right sizes or just find the discount thresholds from your string seller, often a box of ten costs less per unit than a single packet. However, if you do want to buy in bulk you need to be using the strings.
