If you like how the cube feels right now, my recommendation is "don't touch it". If and when you see that the cube starts to lose performance because the lube dries out, there is some cleaning needed, you want to get rid of spring noise in the core, etc. then you can think about disassembling and lubing. I would recommend high viscosity lube for the core (like cubicle weight 5), so that it lasts longer and, depending on your preferences a lower viscosity silicone for the pieces or perhaps Maru lube or a combination of both. Regarding the worries about making the cube gummy, it depends more on the amount of lube you put than the viscosity (of course that also plays a role). So, as it is much easier to add lube than remove an excess of it, I would recommend to start by putting just a tiny bit and adding more later if necessary. This applies both to the core and pieces. I know what I'm talking about as I have a Mini Weilong that still pours lube whenever I take it out of the box

This is a trial an error process so, if you are not sure what "just a tiny bit" might mean in this context I mean a tiny, tiny bit. Like, for example, I have lubed the cores or maybe 8 cubes with less than half a 5cc syringe of weight 5 silicone. That's approx. 15 cubes with 1 sirynge (3 cubes with just 1cc). If you are going to also put Maru in the pieces (it makes the cube very fast but the effect lasts only for some days, a week at most), put just 2 drops in between the pieces and let it spread by randomly scrambling. There are many video tutorials available about how to lube a cube with silicone oil. I just follow more or less Cubeologist's tutorial for
"How to Lube and Tension a MoYu AoLong".