Wrong. I was at the cap in delve league and in betrayal league (yes, after it got changed to 65k which is the current cap IIRC). In delve league it was fairly easy to hit the cap, although it took some time as well, whereas in betrayal league due to the nature of not having sulphite in every map it took fairly long to hit the cap. regardless, whenever I hit the cap it was never enough to delve for more than like ... an hour or so? maybe 2? even at relatively low depths where my routes did take only something between 600 and 1200 or so... I delve rarely takes longer than one minute, plus maybe another minute for whatever event there is at the end. 2 minutes per delve, that's 30 an hour, 1k average cost per delve on medium deep levels, something between 150 and 200 I believe this is, that's almost exactly 2 hours of delving until you run out of sulphite. And running 150-200 depths definitely happens before you hit the 65k sulphite cap, so since earlier than that the cap is lower and later than that the average cost per delve is higher, I would be surprised if people on average can even delve for more than one hours at a time until they run out of sulphite again.

now what happens currently if you have run out? a T15 map (maybe also lower, let's assume T12-T15 grant the same, which is a generous assumption) with niko gives you three nodes at average 1.5k~ish  sulphite, so 4.5k per niko map, that is about 15 maps until you are again at cap (realistically it's even more, but let's just go with that). You have a 20% (?) chance to spawn a master in a map and there is a 20% chance that it will be niko, so in total every 25th map you will get niko (is this math correct?). so every 375 maps you cap your sulphite on average. even if my math somehow is not correct... let's assume you actually get niko every third map (which is completely unrealistic), you would need about 45 (50 for easier calculation, still unrealistic) maps to cap out on sulphite. an average map for an average fast build easily takes about 5 minutes to clear. that is even without breaks more than 4 hours of mapping just to cap sulphite. and then the sulphite is gone in another hour. if the 375 maps are correct, that would mean over 30 hours to cap sulphite which then is gone in 1 hour of reasonably deep delphing. if you would buy gilded sulphur scarabs for every map you would still need 9 of them (= almost 700c), and you would still take almost an hour for the maps just for the sulphur being again gone in the hour after that.