Soaking in the bath for a long time; taking a long, leisurely bath (commonly used as 'to soak for a long time').
疲れた日はつい長湯してしまう。
On tired days I end up soaking in the bath for a long time.
長湯はのぼせることがあるから気をつけてください。
Be careful with long baths because you can get lightheaded.
祖母は長湯が好きで、毎晩ゆっくり入る。
My grandmother likes long baths and soaks slowly every night.