Complex sentence: The skin cover on an umiak will last for two or three years, as does an aluminum boat used in the same way; however, replacing the skin on an umiak is much easier than repairing an aluminum boat.
Split into simpler sentences: The skin cover on an umiak lasts for about two or three years, as does an aluminum boat used in the same way. However, replacing the seal skin on an umiak is much easier than repairing an aluminum boat.