I have noticed that a tire filled with CO2 after a day or two will be soft. When I first used a CO2 pump many years ago I found that a 12g cylinder wouldn’t pump a high pressure road tire up high enough so I carry 16g. I mostly use a mini pump these days, but I’ve never had a tire go soft on ride after CO2 except for operator error.
__________________
N = '96 Colnago C40, '04 Wilier Alpe D'Huez, '10 Colnago EPS, '85 Merckx Pro, '89 Merckx Century, '86 Tommasini Professional, '04 Teschner Aero FX Pro, '05 Alan Carbon Cross, '86 De Rosa Professional, '95 Gios Compact Pro, '95 Carrera Zeus, ‘81 Masi Gran Criterium, ‘81 Merckx Pro, ‘89 Cinelli Supercorsa, ‘83 Bianchi Specialissima, ‘VO Randonneur, Ritchey Breakaway Steel, Rivendell Rambouillet, Heron Randonneur, ‘92 Ciöcc Columbus EL