If it ran the same usage pattern on 1 charge that now takes 2 charges to run, it's suggesting that the battery is going bad. (Normal use for long life consists of keeping the battery between 40% and 80% - never fully charge it.)
If you just want to know if it's bad to charge the battery twice a day, no. Battery life is determined by the amount of charge, not the number of charges. (In fact, one way of ensuring longer battery life is to root with Magisk, then use the Magisk Charging Switch to keep the battery at around 65% to 75%. [It starts charging if the battery drops below 65% and stops charging at 75%. So you can leave the charger plugged in all day and never over- or under-charge the battery.] I don't know if Magisk works with the S8, but the idea is the battery charging situation.)