As I have pointed out previously, and will do so again, the notion of Teutoberg as the dramatic battle that halted the progress of Roman imperialism into Germania is largely erroneous -- the product of the mythology of 19th century German nationalism and romanticism. Rather like Carrhae in the popular conception, it has mistakenly come to be seen as a decisive break in Roman expansionism, and rather like Carrhae, it is a largely erroneous conception.
What the battle of Teutoberg Wald did do was halt the drive of Augustan expansionism into Germania and the Danube basin, and possibly lead to a temporary halt of expansionist momentum across the entire Empire. Yet a mere couple of years later, Germanicus Iulius Cæsar conducted large scale punitive expeditions in the area, Titus Flavius Domitianus conducted operations in the Agri Decumates and against the Chatti, Marcus Aurelius campaigned extensively in the massive Marcomannic Wars, and planned the annexation of Sarmatia and Marcomannia as imperial provinces. As late the early third century Caracalla conducted a massive campaign in the Agri Decumates and in Germania Magna against the Alammani, and Maximinus Thrax also conducted large scale operations in Germany, and even planned the annexation of the entirety of Magna Germania. The recent archeological findings at Kalefeld, in fact quite close to the Teutoberg Wald, display an extensive battlefield with over 1,000 Roman soldiers, including archers, cavalry, and a large quantity of artillery pieces, and seem to posit a date between 230 to 235 AD, when it is known that Maximinus Thrax conducted his German campaign. Fundamentally, Teutoberg did not have such a massive impact on the advance of Roman imperialism in Germania.
It should also noted that although the Elbe, or even the much touted Vistula-Carpathian-Dniester border line might appear superior on paper, the armies and legionary garrisons on the Rhine could be more easily and rapidly supplied from the Mediterranean via the Rhône and Moselle rivers, with only a brief stretch of portages. Armies on the Elbe would have to be supplied from the hazardous North Sea, or by extensive overland routes. Economically, the Rhine basin was already supporting towns and sizeable villages at the time of the Gaius Iulius Cæsar’s conquest of Gaul . Magna Germania and the Elbe basin, however, was far less developed, possessed few villages, and had little food surplus. Thus the Rhine was both significantly more accessible from Rome and better equipped to supply sizeable garrisons than the regions beyond. This is extremely significant, in that prior to the mid third century, Germania was far more poor and underdeveloped in comparison to the Mediterranean basin and Gaul, and that consequently, the Germanic tribes were able to conduct lengthy guerrilla conflicts without substantial harm to the infrastructure. Although the annexation of Germania is clearly sensible in a retrospective “grand strategy” sense, it was quite clearly not worthwhile in the first to third centuries.
It should also be noted that although Germania Magna was never annexed and provincialized, the Romans still exercised substantial control over the region through the cheaper method protectorates, loyal client-kings, and forward legionary garrisons. Germania in the first through early third centuries should not be regarded as a barbarian wasteland entirely divorced from the Roman Empire, but something rather like the north-western frontier of the British Indian Empire. Rather like the Raj, the Roman Empire exercised light control over Germania through frequent punitive expeditions, military garrisons, and loyal client-states.