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In the final stages of stellar evolution low- to intermediate-mass stars losetheir envelope in increasingly massive stellar winds. Such winds affect theinterstellar medium and the galactic chemical evolution as well as thecircumstellar envelope where planetary nebulae form subsequently.Characteristics of this mass loss depend on both stellar properties andproperties of gas and dust in the wind formation region. In this paper wepresent an approach towards studies of mass loss using both observations andmodels, focusing on the stage where the stellar envelope is nearly empty ofmass. In a recent study we measure the mass-loss evolution, and otherproperties, of four planetary nebulae in the Galactic Disk. Specifically we usethe method of integral field spectroscopy on faint halos, which are foundoutside the much brighter central parts of a planetary nebula. We begin with abrief comparison between our and other observational methods to determinemass-loss rates in order to illustrate how they differ and complement eachother. An advantage of our method is that it measures the gas componentdirectly requiring no assumptions of properties of dust in the wind. Thereafterwe present our observational approach in more detail in terms of its validityand its assumptions. In the second part of this paper we discuss capabilitiesand assumptions of current models of stellar winds. We propose and discussimprovements to such models that will allow meaningful comparisons with ourobservations. Currently the physically most complete models include too littlemass in the model domain to permit a formation of winds with as high mass-lossrates as our observations show.

Measuring The Mass Loss Evolution at The Tip of The Asymptotic Giant Branch