There's something about bass players that sets them apart from guitar players when it comes to strings. A lot of bassists really dig old, dead strings! I understand why, don't get me wrong: all you have to say is 'Jamerson' & that old, thick, funky round-sound comes instantly to mind. James Jamerson reportedly never changed the strings on his iconic '62 Jazz Bass & obviously -it sounded GREAT! I've also heard many stories from bass playing colleagues over the years about a special old set of strings that they value more than the bass they're installed upon... (Actually, I have an old set just like this, I'll wax poetic about that later-) BUT honestly, for me, new strings are a necessity in most professional situations! (Sorry old-school purists, but hear me out before you burn my effigy!)
If I've settled upon an argument for new strings (see below what exactly I mean by "new"). It's probably best summed up thusly: "I can easily make a new string sound convincingly 'old' but I haven't yet found a way to make an old string sound convincingly 'new'!" Yeah, yeah, yeah- I know there's no way to make a brand new string feel and sound exactly like a 20-year old set of flatwounds, but I can get close enough that no one's going to be able to tell above the cacophony of those darned electric guitars! ;-) A little careful eq (via my homemade "super-secret" passive tone box - details coming soon...) and attentive right hand technique & I can make my freshly-strung Jazz Bass sound old-school in a heartbeat! Plus, I can pivot on my heels and have a bright, modern 'stringy' sound ready to go without ever putting the instrument down! That's the benefit of a fresh string, baby!
Now what exactly do I mean about "new" strings? Well, honestly, I usually don't love the sound of bass strings just minutes after installation. I'd estimate it takes me (with my technique and less acidic sweat) an hour or two of playing time on a set of Nickel Roundwounds before I think they're in the 'perfect' state: Bright and modern, but with a full fundamental and stable in terms of tuning. Flatwounds are an exception, in my opinion - they sound great at first, but keep getting better for months! Eventually flats settle into a pretty perfect equilibrium before they just get too stretched out to intonate well. Depending on playing frequency and environmental factors (hot summer festival sets come to mind with sweat pouring all over the poor defenseless strings!), I'll probably change most of my roundwound-strung basses every 3 or 4 months. Flatwounds, on the other hand, last at least 2-3 years or more for me (sometimes, much more!). I love flats, but they just aren't perfect for as many styles/genres/situations as roundwounds are.
As you may already have noticed- I am an enthusiastic D'Addario string endorser! I've been given strings at one point or another by just about every major string manufacturer, but I keep going back to D'Addario's. They have a reliable, very consistent product and make just about any kind of string for any instrument. I use a wide variety of D'Addario's starting with my favorite all-purpose "go-to" XL Nickel Roundwound bass strings. D'Addario Chromes are my flatwound of choice for their incredible stability and bright, scooped tone when settled in. I've just recently started experimenting with D'Addario Halfrounds on my hollowbody Ibanez (see Gear Review: Ibanez AGB140 Bass) & I really dig them! I've also switched over to a new product on my acoustic bass guitar: D'Addario EXP Reds coated copper-plated strings (available soon): An outstanding coated string with a distinct "earthy" sound! Watch for a column on my heavily modified Epiphone Rivoli using D'Addario Black Nylon Tapewounds, they really should be the standard string on any short-scale hollowbody bass! I also use a variety of other D'Addario guitar strings such as Pro-Arte' classical nylon strings, EXP 16 coated acoustic strings and various XL Nickel Roundwounds for electric guitars.
There's only one special case in my instrument arsenal that has "old" strings on it - a 1978 Fender maple-board fretless. For whatever reason, the decades old monel-steel flatwound strings tht came on it just work great on that particular instrument. I actually re-strung the bass when I bought it, played it with the new strings for a couple of days & then fished the old strings out of the trash! There's just some weird x-factor with that bass & those old, dirty strings that works best.
Bottom line? New bass strings just have more tonal options than old bass strings. In an industry that demands a chameleon-like ability to jump from old-school to new-school sounds at the drop of a hat, new strings make it possible!