As Clark Griswald said alot of things to consider. Inulate now and if
you replace the unit size it with future insulation factored in the
calculation. Is boiler and piping insulated, are vents old and hiss.
You don`t want this as vap[or escapes requiring makeup water. Does
boiler require makup water every cycle? , Not good. Is heat even. Steam
needs attention for set up and maintenance and can throw off efficiency.
You need a good tech and need to learn your system. 1 1/2 hrs is to
long to generate steam.