You use lengthy to describe an event or process which lasts for a long time. a lengthy meeting. the lengthy process of filling out passport application forms
relatively long in duration; tediously protracted; "a drawn-out argument"; "an extended discussion"; "a lengthy visit from her mother-in-law"; "a prolonged and bitter struggle"; "protracted negotiations"
drawn-out: relatively long in duration; tediously protracted; "a drawn-out argument"; "an extended discussion"; "a lengthy visit from her mother-in-law"; "a prolonged and bitter struggle"; "protracted negotiations"