Just to be clear from the very beginning:
3rd-3rd is a no-no in Standard Mandarin Chinese
The following are the values to be expected in a pitch analysis:
- full 3rd tone: 214.
- half 3rd tone: 21.
- 3rd tone before another 3rd tone: 35 or, as I prefer to clarify, 14, that is close to a 2nd tone, (see Note 1 below).
A third tone should generally be pronounced as a full third tone whenever it is the last syllable in a word/expression. Is that true even when speaking quickly, meaning the final third tone of a word is quickly followed by a non-third tone? Or should it be a half third tone in that case?
A 3rd tone followed by a 1st, 2nd, or 4th tone changes into half 3rd. If it is followed by another character, it means that it is not at the end of the word (spelled alone), phrase, or sentence.
What about the following examples of multiple third tones: 使馆里，大使馆里，地铁里? or 米老鼠我不太喜欢？ These don't quite fit any of the categories above. How should the tones be altered (if at all)?
- 使馆里: shíguán lǐ
- 大使馆里: dàshíguán lǐ
- 地铁里: dìtié lǐ
About the longer sentence, there is more than one possibility.
方法一: Fast reading (see Note 2 below).
- 米老鼠我不太喜欢: míláoshú wǒ bú tài xǐhuānmíláoshúwǒbútàixǐhuān (我 and 喜 are half 3rd)
- or, as many would prefer, mǐláoshúwǒbútàixǐhuān
方法二: 以停顿为分界线 (see Note 3 below).
- 米老鼠我不太喜欢: mǐláoshǔ/wǒbútàixǐhuān ("/" indicates 停顿)
And your last example:
- 我们随时都可以组团: wǒmen suíshí dōu kéyí zǔtuán (我 and 组 are half 3rd)
Variation: since 以 in 可以 is often pronounced toneless, the sentence can also be read:
wǒmen suíshí dōu kéyi zǔtuán
P.s.: In general, some little variations (as, for example, 3-2-3 instead of 2-2-3) are possible, but never, never should two 3rd tones stay together.
Note 1: As explained by Professor 赵兵 a 3rd tone before another 3rd tone "只升不降了，换句话说，21没有了，只升一下14了，往上升了，有点近似阳平声。"
Note 2: According to the article 上声的变调 "(3) 多个上声相连时，“化整为零”，再依上述规律变调。在快读时也可以只保留最后一个字读上声原调，前面的上声字一律变成阳平。 例如： “我找/小组长。 可读为” “wózhǎo/xiǎozǔzhǎng.”也可读为“wózháoxiáozúzhǎng.”。"
Note 3: As explained at https://baike.baidu.com/item/%E5%81%9C%E9%A1%BF/8832419 "停顿，一般指说话中话语的短暂停歇。(或声音的断和连）。朗读停顿有两种：一是句间停顿，就是根据标点符号来确定句与句之间停顿的长短，语调的抑扬；一是句中短暂停顿，它是以词或词组为单位，根据句子成分之间的内在关系来划分的语气停顿。"
About 以停顿为分界线, here is a fantastically well read example: 绕口令练习视频