I do them after writs everytime otherwise its just a problem piling up for me

I only keep clothing and jewellery, and do them when I have 5 for that zone

I say 3-5, then I might do others in the zone if easy to get to even if single.
Some who is far from wayshrines often get get higher numbers.
South east in Shadowfern, the alchemy one north in Malabal Tor.
Who was funny as I did not know it was an location or an quest there before I got an survey there

About five to ten of each kind. I end up sitting on more treasure maps than surveys because the numbers throw me off, I don't remember which map goes with which spot, and being on console its a minor nuisance to look them up.

I don't think I ever have more than 5 on a given character. I pick them up either when I'm in the area, when I wait for something (like guildies to gather for an activity) and have time to kill, or when it's an endeavour (gather 8 such&such, that's 6 done, and probably the remaining 2 on my way there).

I do them immediately now (or at least within 2-3 days, if I don't have time to do them instantly) not to clutter my inventory anymore. Before that, they sometimes stacked for a few weeks and I had about 3-7 each. I always found running back and forth at one spot for the respawn annoying and dead boring.

Currently without eso+, so I'm doing none of them. Sometimes I just destroy the inconvenient ones, especially if there's only one. When Craglorn and Wrothgar were the only ones to go to, it was done daily. I was also less rich in materials then, so the need was more immediate. The only ones I have any real desire to get are the jewelry ones, and I'm even starting to get enough cushion on those supplies as well.

I've stopped doing daily crafting writs both because I have enough reserves to weather a bunch of gear changes and I'm tired of it. Part of the return on your writs is surveys, and if you skip them your supplies have no income. So I'm breaking the cycle and wasting less time in game doing chores.

I really, really wish I could sell them or consolidate them like Aetherial Ambrosia uses up your Psijiic recipe.

Not necessarily and exact survey amount. But, what I usually do is store purple clothing and all jewelry I want to decon in my bank, along with surveys and treasure maps. I decon those items whenever my bank gets over 400 slots used. Once my bank is over 400 slots used even after deconning the purple stuff, I then do my surveys and maps.

Without those things in my bank, I usually sit around 240-250 full in my bank. So 150+ slots of surveys and maps before I do them all. Usually every 3 months or so. And often while I am queuing for BGs or dungeons.

all of them

Hold khajiit's skooma. (That number is 7847)

On all my various accounts and platforms (PC NA, PC EU, XBox NA), close to 10k.

#StackingSurveys4Science Largest stack currently: 149.

I'll do them when

1. There's an endeavor for harvesting nodes from the world or collect survey report
2. The market price of mats is over the gold reward of crafting writs
3. I'm going to turn off my ESO+ for a while and I want to fill the craft bag.
4. I run low on mats for crafting writs and I can't find any on my guild traders or the local traders in my crafting area. If I have to leave the area to get more, I might as well collect surveys for free.
5. I've done my writs and waiting in a queue.

If you use LazyWritCrafter, you can use the command /countsurveys to tell you how many surveys of each profession you have in your inventory and your bank.