Lidl and Tchibo give exactly the same service apart from the different pricing and the fact that Lidl do have an additional limit of 500MB/day besides those 5GB/day.
Subscriptions to Tchibo's data options will only recur if there's enough credit left at the end of the billing period or if you recharge enough credit within 48 hours after the last billing period has finished.
With Lidl subscriptions to data options do also recur but afaik you don't have these 48 hours grace period to reload. So you would have to manually resubscribe to your data option if it could not be prolonged due to the lack of credit.
Anyway you are not obliged to recharge. If your data option is not being prolonged this doesn't affect your account and your SIM will still remain active. You can recharge even months later and resubscribe to a new data option.
Regarding your question of subscription and cancellation of data options within a month, this is simply impossible as you can't switch data options within the current billing period. You may cancel your data option but this will not take effect before the current billing period has ended.
BILDmobil are the only MVNO I know, who offer a data packs with longer validity, namely 5GB valid for 90 days for € 40 (see
BILDmobil Daten-SIM ? Prepaid-wiki), but they are on the Vodafone network where VoIP is actually being blocked.