If you're using a static group you'll indeed need to manually remove the computers that no longer need the package manually from the group.
You could instead deploy based on a report that for instance only shows computers that don't have X software installed. I've added an example report below of a report that lists all computers that do not have Notepad++ installed. This report can be adjusted for any other software.
Select Top 1000000 tblAssets.AssetID,
tblAssets.AssetName,
tblAssets.Domain,
tblAssets.Username,
tsysAssetTypes.AssetTypeIcon10 As icon,
tblAssets.IPAddress,
tblAssets.Lastseen,
tblAssets.Lasttried
From tblAssets
Inner Join tblAssetCustom On tblAssets.AssetID = tblAssetCustom.AssetID
Inner Join tsysAssetTypes On tsysAssetTypes.AssetType = tblAssets.Assettype
Where tblAssets.AssetID Not In (Select Top 1000000 tblAssets.AssetID
From tblAssets Inner Join tblSoftware On tblAssets.AssetID =
tblSoftware.AssetID Inner Join tblSoftwareUni On tblSoftwareUni.SoftID =
tblSoftware.softID
Where tblSoftwareUni.softwareName Like '%Notepad++%') And
tsysAssetTypes.AssetTypename = 'Windows' And tblAssetCustom.State = 1
Order By tblAssets.Domain,
tblAssets.AssetName